Archive-name: AudioFAQ/part1 Last-modified: 1993/8/23 Version: 1.8 1.0 Contents: Part 1: 1.0 Contents 2.0 Organization 3.0 Purpose 4.0 Omissions 5.0 Credits 6.0 Errors and Corrections 7.0 Disclaimer 8.0 Copyright Notice 9.0 Speakers 10.0 Amplifiers Part 2: 10.13 Amplifiers (continued) 11.0 CD Players, CDs, Turntables, and LPs Part 3: 12.0 High Fidelity Systems 13.0 Listening Rooms and Houses 14.0 Recording 15.0 Mail Order Part 4: 16.0 Wire 17.0 The Press 18.0 Retail 19.0 Miscellaneous 20.0 Net Protocol 2.0 Organization: This FAQ is divided into a preamble and a list of subjects. Each subject is described by a list of questions and answers. Some questions have no answers yet. That's life. This FAQ is split into four individual postings. This FAQ also references a frequent posting of sources for audio via Mail Order. That list is maintained by nau@SSESCO.com (William R. Nau). Contact Mr. Nau directly for information or corrections to that posting. The list is also available via FTP in the pub/rec.audio directory of SSESCO.com. Lines beginning with "|" are new since the last version of the FAQ. 3.0 Purpose: The purpose of this FAQ is to address frequently-asked questions as a whole, so that rec.audio volume can be reduced. Towards this end, we assembled a list of common questions, and some general answers to these questions. Audio is part science and part art, so some of the answers are objectively correct, while others try to open-mindedly present both sides of a subject. 4.0 Omissions: Many valuable things have been left out of the FAQ. In part this is because there is just too much to say about audio. In part, this is because the general reader doesn't need that much detail. Also, some things were omitted because they are too controversial or inflammatory. 5.0 Credits: This FAQ is the work of many people. Allow me to thank everyone who helped now. We appreciate all of your contributions. However, all blame and criticism should go to Bob Neidorff at neidorff@uicc.com. Some of the contributors to this FAQ are listed below. Others have made great contributions, but are no less appreciated. andrew@research.att.com (Andrew Hume) jj@research.att.com (jj) neidorff@uicc.com (Bob Neidorff) Rick Oakley (no internet access) DPierce@world.std.com (Richard d Pierce) P.Smee@bristol.ac.uk (Paul Smee) gmw1@cunixa.cc.columbia.edu (Gabe M. Wiener) 6.0 Errors and Corrections: Some errors are intentionally included in this FAQ. (It's easier to say that and later admit we were wrong, than to claim that this is a best effort). If you have a correction to the FAQ, additional information, or a new topic for the FAQ, please send e-mail to neidorff@uicc.com describing your thoughts in detail. Please include your e-mail address in your submission, so that we can stay in touch. Every submission will be considered for inclusion in the next release of the FAQ. This FAQ will be reposted every month. 7.0 Disclaimer: Everyone's human. Nothing is perfect. The people who wrote the information here put varying amounts of research into their work. To the best of my knowledge, no one made any contribution or comment because of a vested interest. Audio is a very lucrative and competitive industry, filled with honest companies, aggressive marketing people, people who stretch the truth very thin, excellent products, and lousy products. We tried hard to screen the hype from valuable data. If we insulted, omitted, or otherwise disturbed you, your company, your product, or something you feel strongly about, please let me know. The information here attempts to paraphrase a large portion of the information exchanged on rec.audio. At times, people will make recommendations or suggestions to others on rec.audio. Some of these statements are included here because we have been asked to include statements of that sort. These statements, and everything in this document is the opinions of various people. Nothing here is intended as recommendation or suggestion. Further, no matter how it is worded, nothing here should be taken as fact. The authors take no responsibility for any use of this information. 8.0 Copyright Notice: The information contained here is collectively copyrighted by the authors. The right to reproduce this is hereby given, provided it is copied intact, with the text of sections 1 through 8, inclusive. However, the authors explicitly prohibit selling this document, any of its parts, or any document which contains parts of this document. 9.0 Speakers: 9.1 What should I listen to when evaluating speakers? The most important thing is to listen to recordings that you *know*. Any good salesman will play you recordings that highlight that particular speaker. Do not be embarrassed about bringing a stack of CDs with you to the hi-fi shop. Do not spend your valuable listening time switching between a dozen pairs every 3 seconds. If you are shopping at a quality store, the dealer will, from the description of your room, your size requirements, your musical tastes, and your budget, be able to show you a couple of pairs that will be close to what you want. Spend several minutes listening to each. When you think you're close, don't be embarrassed about spending half an hour or more listening to the speakers. You're going to have them in your home for a lot longer, and many speakers will cause "listening fatigue" after a short time. Make sure you really like them before you hand over money. One thing to try is well recorded "Spoken Word" records; most people have a very good ability to tell when a speaking voice sounds unnatural, even if they've never heard the person speaking live. If you play an acoustic instrument, find something that features that instrument solo, or in a small group; make sure it really sounds like it should. Almost everyone has heard a live piano. Piano can be very revealing. Blues, jazz, folk, or 'easy listening' music with simple instruments and a female vocalist is also revealing. Well done female singing voices provide a very good test of a system's response. Try something simple and soft, which will let you hear any noises coming from the system; and something complex, with lots of instruments all happening at once, to make sure the system doesn't go muddy when things get complicated. And, of course, try a few of your favorites, and see if you like what happens with them. If a sales person suggests some music to listen to, the odds are that it isn't the most revealing. Sales people tend to suggest things which sound great. Anything you own and like is good, because you know it and are happy to listen to it carefully. No matter how good the recording, if you don't like Opera, you won't listen to it as carefully as your favorite, scratchy, 1940's rhythm and blues. Most important is to listen to something you are familiar with. Even if a recording is flawed (and what ones aren't?), how is it different from your normal setup? Some of the most important differences are "Gee, I never heard that instrument before!" 9.2 What should I listen for when evaluating speakers? When comparing two speakers side-by-side, doing an AB comparison, be extremely careful to match the levels before evaluating. A slight level difference can make one speaker sound better, even though the difference may not be perceived as a level difference. Some claim that you will be influenced by a difference of less than 1/2 dB! First and foremost, the sound should be natural. If you listen to vocals, close your eyes and try to picture someone singing in the same room with you. Does it sound realistic? Likewise with instruments. You selected recordings of instruments that you like and have heard live. Do they sound like what you remember them sounding like live? Your very first impression should be something like "what nice sound". If your initial gut reaction is "gosh, what a lot of detail", the system is likely to be heavy in the treble (often interpreted by beginners as "more detailed") and you'll probably find that annoying after a while. If your first reaction is "hey, what powerful bass", then the system is probably bass-heavy, rather than ideal. The most common mistake for beginners is to buy a system with REALLY powerful bass, because it sounds "impressive" at first. After a while, though, you'll get tired of being thumped on the head by your music. Not to say that good bass and treble aren't important. But your first realization should be that the music is all there, and that it comes together as good music, without one particular part trying to dominate it. Sit back and listen to it for a bit. You should be able to pick out the individual instruments if you want. They shouldn't force themselves on you, and you should also be able to hear the music as a single piece, the sum of its parts, without feeling like each of the instruments is trying to grab your attention away from the others. You should check how things sound with the amp turned up, and also with it turned down to a fairly low volume level. Some speakers which sound very nice at low levels begin to sound confused, like they can't cope, when turned up. On the other hand, some sound nice loud, but sound thin and bodiless when you turn them down a bit. With the spoken word or female vocalist, listen for "sibilance", a pronounced 'hiss' at the end of 's' and 'z' sounds. It shouldn't be there. Most planar speakers just can't play very loud. Whatever you hear, do some auditioning at the maximum volume you anticipate ever wanting. It is acceptable and sometimes desirable to switch the stereo to mono to evaluate naturalness. Mono is a good test of both the room and the speakers. The image should be rock-solid dead center, and not move with signal or level. If it isn't perfect mono, it will be nearly impossible to create a good stereo. A speaker in a large box is capable of producing low frequencies at higher volumes with more efficiency than a small box, but that doesn't mean that a small box can't have great bass, it just won't be as efficient and can't play as loud. Good speakers can "recreate a natural stereo sound stage", placing some instruments to the left of the left speaker, some sounds in the middle, and some to the right of the right speaker. Poorer speakers make it harder to localize voices. 9.3 Why use a subwoofer? Will it help? One or two? One reason to get a subwoofer is to add bass to a feeble system. A second reason is to move the lowest frequencies to a separate driver, and thereby reduce a particular kind of distortion caused by the nonlinear mixing of different sounds, called "intermodulation distortion". A third is to increase the power handling ability of the system and the overall reliability. All are valid reasons, but it isn't so simple. To improve the sound of a good speaker system, a subwoofer must "integrate smoothly" into the system, extending the bass without causing peaks or dips. Many subwoofers have a crossover that goes between your amp and your main speaker which sends the lows to the subwoofer and sends the higher frequency signals to the main speakers. This may damage the perfect sound of a good system, it may sound similar, or it may sound better. Most good small speaker systems have a bass peak at resonance, which attempts to compensate for the absence of lower bass. Like it or not, this is the only way to make a small system sound realistic. If the small system is done well, the improvement you will get from a subwoofer will be small, but still real and, to many, significant. Correctly done, a good subwoofer will enhance the sound of a good small-box system. Done wrong or haphazardly, anything is possible. Even a fine large speaker system might benefit from careful addition of a subwoofer. However, the better the original system, the more likely it will be that a modest subwoofer will do more harm than good. Low frequencies travel less directionally than high frequencies, so many people say that only one subwoofer is required for good sound. This is true to some extent, but not completely true. There are a few reasons for getting two subwoofers. Some feel that you need two subwoofers to accurately reproduce the stereo image, no matter how little low-frequency stereo information there is. Others feel that two subwoofers are much easier to set up in a room, less likely to excite standing waves in the room, and give smoother sound. A third reason is that two subwoofers can produce twice the sound of one. Finally, even though subwoofers produce very low frequency sound and very low frequency sound is non-directional, subwoofers also have output at 100 Hz, and sound at 100 Hz is directional, so two subwoofers will give a slightly better stereo image than one. Assuming, of course, that the two are separated by at least two feet. Finally, even though original source signals rarely contain any music with stereo components below 50Hz, there may be some noise component with low-frequency out-of-phase noise. This unusual noise might add a sense of space to a recording if it is reproduced by a system in which the woofers are very far apart. It is still true that a single good subwoofer, correctly added to a system will help the sound but two will probably help more. 9.4 How do you connect a subwoofer to a stereo? Many subwoofers contain their own amplifier and crossover. For these, take the preamp output and feed it into the subwoofer amp input and also into the main amplifier. For other subwoofers, just run them in parallel with your main speakers, or combine them into your system with your own bass amplifier and crossover. Some A/V receivers contain a splitter specifically for use with subwoofers. If you have one of these, you will either want a separate amplifier for your subwoofer or an amplified subwoofer. Consult the manual which comes with the subwoofer. 9.5 What do I need for surround sound? "Surround Sound" has referred to a number of different products over the years. Many mass-fi receivers have "Surround Sound" buttons that do little more than muck up the imaging. In recent years the term "Surround Sound" has become synonymous with the surround systems produced by Dolby Laboratories. Dolby Surround comes in several flavors, such as passive surround (which simply decodes the phase information and sends it to the rear speakers) and the more advanced system called Pro Logic. Pro Logic system uses computer circuitry to route directional information to the appropriate speakers. Generally, one needs at least two more speakers beyond the main stereo pair. Advanced Pro Logic systems such as the Lexicon and Fosgate can accommodate several more speakers beyond the two additional ones (usually placed in the rear). Often one can find Pro Logic systems with two front, two rear, two side, as well as a center channel speaker for dialogue. 9.6 I was just approached (accosted?) by a couple of kids driving a van that said they had some GREAT speakers to sell. They are overstocks, used by major recording studios and DJs or even hot, and they normally sell for $1000/pr, but they'll let me have them for just $399. Am I getting ripped off? Yes, you most certainly are. The speakers these people sell are none of what they describe. They are never used in studios. There might be one or two DJs out there that use them because they can't afford anything else. They are not overstocks, and in all likelihood, they are NOT HOT!. Are they good speakers? No, they're, at best, no better than the big boom boxes you find in $400 rack systems in department stores. They are worth no more than what the kids paid for them ($100/pr). The speakers go under names like "Acoustic Monitor DB IV", "Acoustic Linear," "Pro-Poly," "Audio Reference 4350" and so on. They all "feature" things like "liquid cooled 3" tweeter", poly-cone 12" woofer, fantastic (but impossible) frequency response, 98 db/watt sensitivity, and so on. These speaker are made by a couple of manufacturers with the intent of being sold exactly this way. They cost the kids in the van about $100 a pair, and the kids are given minimal training about what kinds of stories to use, what parking lots are the most likely to generate sales (department store parking lots near colleges in September is a great time for these guys). Anything over and above the $100 dollars the kids paid is pure profit (except for gas money). Stay away, you're getting ripped off. 9.7 What speakers should I consider in the $XXX/pair price range? This is probably the most commonly asked question on rec.audio, and also the most impossible to answer. The market keeps changing, everyone has different tastes, and no one has the time to listen to even 10% of the products available in any country. Also, many good products are only available in specific regions or countries. If you really want recommendations and are willing to listen to the opinions of others, check the past few issues of Stereophile Magazine. Although they are strongly biased towards very expensive gear and have their own particular other biases, they do steer you to some very good equipment in their frequently-updated list of "RECOMMENDED COMPONENTS". 9.8 Can you build better speakers than you can buy? Some people can build better than you can buy. These people are either experts, golden ears, extremely well equipped, inspired, or a combination of the above. Some companies have plans available to entice you into buying their drivers: Audio Concepts, Audax, Dynaudio, Focal, KEF, and Scanspeak. Your success rate with these plans will probably be very good IF your cabinetry skills are very good and IF you follow the plans precisely. If you deviate (as everyone does), anything is possible. Stereophile has published three different plans designed by Dick Olsher which are similar two-way ported systems. A recent one of these was in Stereophile Nov '90, pages 94-127. Audio Magazine published a plan called "The Pitts" by Ken Kantor, in Audio, Nov '88 pages 65-71 continued in Dec '88 pages 73-77. This plan is a two-way sealed box. I have built one published design and one manufacturer's design. I believe that both met my expectations. They took me a long time to build, taught me a lot, were fun projects, and sounded good when finished. I also believe that a commercial system which cost what my parts cost will never sound anywhere near as good as the one I build. If you consider $2/hour for my time, however, building is financial suicide. Designing your own system is even more a can-of-worms, and should be left to those with either a strong stomach, a very forgiving ear, infinite resources, or excellent guidance. 9.9 Where can I read more about speaker building? Speaker Builder Magazine Audio Amateur Publications PO Box 494 Peterborough NH 03458 USA 603-924-9464 The Loudspeaker Design Cookbook, Fourth Edition by Vance Dickason (C) 1991 ISBN 0-9624-191-7-6 $29.95 + $2.00 S&H from Old Colony Sound Lab PO Box 243 Peterborough NH 03458-0243 USA 603-924-9464 High Performance Loudspeakers by Martin Colloms Synergetic Audio Concepts Classes and Newsletters Syn-Aud-Con teaches classes on Audio and Acoustics 12370 W. Co. Rd. 100 N. Norman IN 47264 USA 812-995-8212 9.10 Where can I buy speaker drivers? A & S Speakers (Broad line) 3170 23rd Street San Francisco CA 94110 USA 415-641-4573 Audio Concepts (Their own kits plus drivers) 901 South 4th Street LaCrosse WI 54602 USA 800-346-9183 Phil Baker (Surplus cabinets only) 546 Boston Avenue Medford MA 02155 Carbonneau 609 Myrtle NW Grand Rapids MI 49504 USA 616-456-9528 Drexler Audio Systems (Bandor Speaker Distributor) 14 Rose Lane Rosemont PA 19010 Gold Sound (Broad line including pro speakers) PO Box 141 Englewood CO 80151 USA 303-789-5310 Madisound (Broad line) 8608 University Green Box 4283 Madison WI 53711 USA 608-831-3433 McGee Electronics (Polydax, Pyle, Motorola, EV, MTX) 1901 McGee Street Kansas City MO 64108-1891 USA 913-491-5287 or 800-876-2433 Meniscus 2442 28th Street SW Ste D Wyoming MI 49509 USA 616-534-9121 Parts Express 340 East First Street Dayton OH 45402-1257 USA 513-222-0173 Solen Electronique (Airborne, Audax, Ceratech, Dynaudio, Eton, Lpg, Morel, Peerless, Scan-Speak, Seas, Solen, Vifa) 4470 Avenue Thibault St.-Hubert, QC J3Y 7T9 Canada Voice 514-656-2759 FAX 514 443-4949 Speakers Etc. 1828 West Peoria Avenue Phoneix AZ 85029 USA 602-944-1878 SRS Enterprises (Pyle, Pioneer) 318 South Wahsatch Avenue Colorado Springs CO 80903 USA 719-475-2545 Transducer Technology (Cabasse, Accuton, Vieta, Audiom by Focal, Stage, Tekton) 4320 Spring Valley Road Dallas TX 75244 214-991-6994 Zalytron (Broad line including kits) 469 Jericho Turnpike Mineola NY 11501 USA 516-747-3515 9.11 Where can I buy loudspeaker kits? Audio Concepts, Inc. (Wide range of kits. Catalog available) 901 South Fourth Street La Crosse WI 54601 USA 608-784-4570 Fried Products (Parts kits starting $550. Catalog available) (Emphasizes high-end transmission line speakers) (Parts kits have plan, crossover, and driver) Conshocken Road Conshocken PA 19428 USA 215-277-9004 Mahogany Sound (Parts kits and Woodstyle kits) (Parts kits have plan, crossover, and driver) (Woodstyle kits also have 3/4" MDF veneered boxes) (Prices $150/pair to $500/pair. Catalog available) (Two way, three way & subwoofer kits) 2610 Schillingers Rd #488 Mobile AL 36695 USA 205-633-2054 Also see above, under suppliers for speaker drivers. 9.12 How can I improve the sound of my speakers? The best way to change the sound of your speakers is to change where you put them. Ideally, the speakers should be located at ear level, in front of you, squared off between you. It's then a matter of fiddling with a) the angles, b) the distance apart, c) the distance from you, and d) the distance from the wall. Just moving the speakers around in the room or putting them onto stands can make a major difference. For more on speaker placement, see 13.1 below. Other than that, speaker modifications can be a can of worms, or can produce very subtle changes, which you might prefer. For example, you might improve a speaker by adding some cross braces of 1"x1" wood from left to right and from front to back. This will stiffen the cabinet and reduce speaker cabinet wall vibrations, which probably hurt sound quality. Alas, this will be most effective with lower-cost and poorly built speakers. Along similar lines, some claim success putting lead wire or epoxy putty on thin parts of the speaker to damp out resonances. You can try doing this to the thinner parts of the speaker "basket" or frame, or to the front "baffle" or supporting panel. Still another "tweak" is to add sound deadening felt pads to the inside walls of the speaker. Instead of felt pads some advocate sand-filled latex coatings on the inside walls of speakers. Others advocate ceramic tiles held in place with "thinset". Still others rave about commercial products like AC Glop, Acoustic Magic, and Bostik Sheet. However, the people who rave about these products tend to be the same people who sell them. Any change along the lines of adding felt, cross-bracing, or putty will have subtle effects on the sound. For the brave at heart, you can replace old or cheap drivers with better ones, but the results of this one change can be very dissatisfying if you happen to get the wrong type of driver for that application, and may never sound right, even if you use a similar driver. Speaker system design is still somewhat of a science and somewhat of an art. Throwing paint on a canvas often makes a mess. Whatever change you try, don't "burn your bridge" home. Be sure that you can undo whatever change you did, just in case. Many tweaks to good speakers, no matter how well thought through, will correct for one flaw, but create others, or correct a flaw that the designer had cleverly used to his advantage. 9.13 How can I replace/re-cone my old speakers? The best chance of success is to buy an identical replacement speaker driver from the manufacturer of the system. Second choice is to buy the exact same driver from a distributor. This is sometimes difficult because it is hard to learn exactly what driver the manufacturer used. In addition, EVEN IF the manufacturer used stock speakers, they might have used matched pairs or selected speakers by hand for an exact set of specific characteristics. There are companies that rebuild drivers, but they charge quite a bit. I have heard $75 per driver. This is rarely done for anything but very expensive commercial drivers. Speaker manufacturers will often sell owners the materials that they need to repair a speaker. If you are handy with delicate things, it is worth a try. In addition to speaker manufacturers, there are companies which sells rebuild kits for approximately $30 per pair, containing new foam, a special glue, and instructions. If you have a blown or distorted voice coil, this still won't help. A few netters have used rebuild kits from this company successfully. Contact: Stepp Audio Technologies PO Box 1088 Flat Rock NC 38731 USA 800-747-3692 Another vendor of speaker repair parts is: Simply Speakers P. O. Box 22673 St. Petersburg FL 33742 USA 800-767-4041 or 813-571-1245 Some speaker manufacturers have very good warranties. Electro-Voice warranties all professional products for life. KEF has a similarly broad warranty on their speakers. Contact the manufacturer first. 9.14 What computer programs can I use to design speakers? There are many useful programs available, but none are complete without a good knowledge of speaker design. Further, you will NEED to supplement any program with hand tweaking for the best sound. Finally, no simulation program is ever useful without good model parameters, and the parameters which manufacturers give you are often imperfect, so many good designers strongly recommend your own lab measurements. The Loudspeaker Design Cookbook (see 9.9) tells you how to measure a speaker, and also enough theory to feel confident with a good program. You can get a lot done with a simple spreadsheet and the equations in a book like The Loudspeaker Design Cookbook. For more information on speaker programs for speaker design and speaker design hardware, such as measurement systems, get the archive "audio.speaker" in directory "dist" on node "research.att.com" (also known as 192.20.225.2). 9.15 Can I magnetically shield my speakers for use near a TV? You probably will need to buy speakers that are made with an integral magnetic shield. Magnetic shielding is usually done by either shielding the speaker magnet or by cancellation of the magnetic field very close to the magnet, or by both. Shielded speakers are NOT built by lining the enclosure with metal. While it sounds like a good idea, it doesn't work. A common magnet shield is a mild steel cup around the magnet. This is the cheapest shield, and is usually fairly ineffective. It also will interfere with the speaker's critical magnet gap, so this type of shield can hurt speaker performance by shorting the magnetic field and reducing the magnetic flux density in the gap, which can reduce efficiency and affect the speaker's low frequency performance. Cancellation is done using a reverse-polarized magnet glued to the back of the main magnet. If done right, it can almost completely cancel the rear stray field. In some cases it can also increase the magnetic flux density in the gap, which may or may not be desirable. 9.16 What are all of these abbreviations people use for speakers? Most of these parameters are well documented in the Loudspeaker Design Cookbook. (see 9.9) In summary: Fs Driver free air resonance, in Hz. This is the point at which driver impedance is maximum. Fc System resonance (usually for sealed box systems), in Hz Fb Enclosure resonance (usually for reflex systems), in Hz F3 -3 dB cutoff frequency, in Hz Vas "Equivalent volume of compliance", this is a volume of air whose compliance is the same as a driver's acoustical compliance Cms (q.v.), in cubic meters D Effective diameter of driver, in meters Sd Effective piston radiating area of driver in square meters Xmax Maximum peak linear excursion of driver, in meters Vd Maximum linear volume of displacement of the driver (product of Sd times Xmax), in cubic meters. Re Driver DC resistance (voice coil, mainly), in ohms Rg Amplifier source resistance (includes leads, crossover, etc.), in ohms Qms The driver's Q at resonance (Fs), due to mechanical losses; dimensionless Qes The driver's Q at resonance (Fs), due to electrical losses; dimensionless Qts The driver's Q at resonance (Fs), due to all losses; dimensionless Qmc The system's Q at resonance (Fc), due to mechanical losses; dimensionless Qec The system's Q at resonance (Fc), due to electrical losses; dimensionless Qtc The system's Q at resonance (Fc), due to all losses; dimensionless n0 The reference efficiency of the system (eta sub 0) dimensionless, usually expressed as % Cms The driver's mechanical compliance (reciprocal of stiffness), in m/N Mms The driver's effective mechanical mass (including air load), in kg Rms The driver's mechanical losses, in kg/s Cas Acoustical equivalent of Cms Mas Acoustical equivalent of Mms Ras Acoustical equivalent of Rms Cmes The electrical capacitive equivalent of Mms, in farads Lces The electrical inductive equivalent of Cms, in henries Res The electrical resistave equivalent of Rms, in ohms B Magnetic flux density in gap, in Tesla l length of wire immersed in magnetic field, in meters Bl Electro-magnetic force factor, can be expressed in Tesla-meters or, preferably, in meters/Newton Pa Acoustical power Pe Electrical power c propogation velocity of sound at STP, approx. 342 m/s p (rho) density of air at STP 1.18 kg/m^3 9.17 What are fluid-filled (fluid-cooled, ferro-fluid) tweeters? These tweeters are built almost exactly the same as other tweeters. They look and act almost exactly the same, too. The only difference is that they have a small, controlled amount of a special fluid inserted into the gap between the magnet and the voice coil. One big effect of adding this fluid to a tweeter (or to any speaker) is that it makes the voice coil capable of dissipating more heat. This means that the speaker can have a lighter voice coil, for better performance, or a higher power rating for the same voice coil. The other big effect of this fluid is to add mechanical damping. The frequency response and transient response of the driver will change, possibly for the better. In addition, this fluid may help center the voice coil, may lubricate the voice coil, and may help keep dirt out of the gap. This fluid will not increase the magnetic field, concentrate the magnetic field or otherwise change the magnetic circuit. Nor will it cushion impact if the voice coil bottoms. The fluid used for this purpose is often called "ferrofluid". It consists of sub-microscopic particles of magnetic material suspended in special oil. This fluid stays in the gap because of the strong magnetic pull of the magnet. There is some debate over whether these fluids can dry out with time. Manufacturers claim that the oil used is non-volatile. It is possible to use ferrofluids in mid-range drivers and woofers. However, as tweeters tend to have the most fragile voice coils, tweeters have the most to gain from ferrofluid. There are various different fluids on the market, some of which have characteristics tailored to tweeters, some to woofers, etc. It is very risky to blindly add fluid to a driver. It may not be compatible with the adhesives used in the driver, may not be practical with the particular driver layout, and is impossible to remove. Permanent driver damage is possible. 10.0 Amplifiers Note: A receiver contains an amplifier, so the following questions apply to both receivers and amplifiers. In the following text, "amp" and "amplifier" are used synonymously. 10.1 What is Biamping? Biwiring? Most speakers are connected to an amplifier by one pair of terminals on each speaker. Within these speakers, a crossover distributes the signal (modified appropriately) to each of the drivers in the speaker. Some speakers are set up to be either biwired or biamped. A much smaller number allows triwiring and triamping. The same principles apply but use three sets of wires or three amplifiers instead of two. Most speakers that support biamping/biwiring have two pairs of terminals and some mechanism for shorting the two pairs together when used in the normal way. This mechanism is most likely a switch or a bus bar. To help the descriptions below, I will refer to these two pairs as LO and HI (because normally one pair connects to the woofer and the other pair connects to the tweeter/midrange). Biwiring means that a speaker is driven by two pairs of wires from the same amplifier output. One cable pair connects HI to the amp, and the other cable pair connects LO to the same amp output that you connected the HI cable to. Biwiring is controversial; some folks hear a difference, some do not. The most plausible explanation involves magnetic induction of noise in the relatively low current HI cable from the relatively high current signal in the LO cable. Accordingly, Vandersteen recommends the two cable pairs for a channel be separated by at least a few inches. In any case, the effect appears to be small. Biamping means that the two pairs of terminals on a speaker are connected to distinct amplifier outputs. Assuming you have two stereo amplifiers, you have two choices: either an amp per channel, or an amp per driver. For the amp per channel, you connect each terminal pair to a different channel on the amp (for example, the left output connects to HI and the right side to LO). In the other configuration, one amp connects to the LO terminals, and the other amp is connected to the HI terminals. The point of biamping is that most of the power required to drive the speakers is used for low frequencies. Biamping allows you to use amps specialized for each of these uses, such as a big solid-state amplifier for the LO drivers and higher quality (but lower power) amp for the higher frequencies. When you have two identical stereo amps, some folks recommend distributing the low-frequency load by using an amp per channel. In any case, whenever you use two different amplifiers, be careful to match levels between them. Biamping also allows you to use high-quality electronic crossovers and drive the speaker's drivers (the voice coils) directly, without the series resistance and non-linear inductance of a passive crossover. Biamping which uses the speaker's crossover is therefore much less desirable. Replacing a good speaker's crossover with an electronic crossover has advantages, but involves some very critical tradeoffs and tuning which is best left to those well-equipped or experienced. See also section 16.0 below, on wire and connectors in general. 10.2 Can amplifier X drive 2 ohm or 4 ohm speakers? Almost any amplifier can drive almost any load if you don't turn the volume up too high. Tube amplifiers are one exception. Some amps clip if you play them too loud. This is bad and damages speakers. Other amplifiers shutdown if they are asked to play too loud. Many will overheat, with bad consequences. However, in almost all cases, it takes seriously loud sound or low speaker resistance (less than 4 ohms) to do damage. Running two sets of 8 ohm speakers at once with common amplifiers represents a 4 ohm load. Four sets of 8 ohm speakers makes a 2 ohm load. Two sets of 4 ohm speakers also makes a 2 ohm load. If you stay sober and don't turn it up past the point where it distorts, you are PROBABLY safe with most amplifiers and most loads. See 10.3 for more information. 10.3 How do I drive more than two speakers with one stereo amplifier? One amp can drive many speakers. However, there are two limits to this practice. The first is that you can overheat or damage an amplifier if you drive too low of an impedance to loud listening levels. Avoid loading any amplifier with a lower impedance than recommended. Adding two speakers to one amp output loads that output with half the impedance of one speaker. (See also 10.2 above) The second is that with tube amplifiers, which are uncommon in today's common system, it is important that the speaker impedance and the amplifier output impedance be well matched. When driving two or more speakers from one amp output, always wire them in parallel, rather than series. Series connection, while safe in terms of impedance levels, can hurt sound quality by raising the impedance that the speakers themselves see. Many amplifiers have connectors for two pairs of speakers. In general, these amplifiers also have a speaker selector switch. These amplifiers almost exclusively connect the speakers in parallel when both are selected. It is common for these amplifiers to specify 8 ohm speakers only. The reason that they specify 8 ohm speakers is because the amplifier is built to drive either 4 or 8 ohms, and two sets of 8 ohm speakers loads the amplifier as if it were one set of 4 ohm speakers. It is probably perfectly safe to connect one set of 4 ohm speakers to an amplifier with two sets of outputs, provided that you NEVER use the second set for any set of speakers. 10.4 How big an amplifier do I need? Unfortunately, amplifier power ratings and speaker power ratings are almost always misleading. Sometimes, they are factually wrong. Speaker ratings are almost useless in evaluating needs. More importantly, human hearing is sensitive to the log of the power coming out of the speaker. This means that the perceived difference between an 80 watt amplifier and a 100 watt amplifier, all else equal, is very small. (under 1 dB!) There is a wide variation in the "efficiency" and "sensitivity" of the various speakers available. I have seen good speakers with under 80 dB per watt efficiency and have also seen good speakers with over 96 dB per watt efficiency, measured one meter from the speaker. This difference of 16 dB represents a factor of 40 difference in power requirement! So the first step in determining amplifier requirements is to estimate relative speaker efficiency. Other factors include how loud you will want to listen, how large your room is, and how many speakers you will drive with one amplifier. This information will give you a rough starting point. For an example, a typical home speaker will produce 88 dB at 1 watt. In an average room, a person with average tastes will be happy with this speaker and a good 20 watt per channel amplifier. Someone who listens to loud music or wants very clean reproduction of the dynamics of music will want more power. Someone with less efficient speakers or a large room will also want more power. Past that point, you will have to use your ears. As with all other decisions, your best bet is to get some candidates, borrow them from a friendly dealer, take them home, and listen to them at your normal and loudest listening level. See if they play cleanly when cranked up as loud as you will ever go, into your speakers in your room. Of course, it is also important to be sure that the amp sounds clean at lower listening levels. 10.5 Do all amplifiers with the same specifications sound alike? Some say that they do. Some say that they don't. Some demonstrated that many amplifier differences can be traced to very slight frequency response difference. Let your own ears guide you. If you want to compare amplifiers, you can do it best in a controlled environment, such as your home, with your music and your speakers. Also be very careful to match levels precisely. All you need to match levels of amplifiers is a high input-impedance digital voltmeter set to AC volts and a test recording or signal generator. 10.6 Is this amplifier too big for that set of speakers? There is no such thing as an amplifier that is too big. Small amplifiers are more likely to damage speakers than large ones, because small amplifiers are more likely to clip than larger ones, at the same listening level. I have never heard of speakers being damaged by an overly large amplifier. I have heard of 100 watt speakers being damaged by a 20 watt | amplifier, however, in really abusive hands. This will happen | because when an amplifier clips, it will generate much more | energy at high frequencies than normal music would contain. | This high energy at high frequencies may be less than the | continuous power rating of the speaker, but higher than the | actual energy rating of the tweeter. Tweeters tend to be | very fragile components 10.7 Where can I get a cheap low-power amplifier? There are very few available. One source is to buy a cheap boom box and only use the amplifier. Another source is Radio Shack. A third alternative is to buy a car stereo booster and get a 12V power supply for it. Finally, you can build an amp pretty easily if you are handy, but it probably won't be that cheap. Mark V Electronics, for example, sells 20 watt amp kits for under $30 and 80 watt amp kits for under $150. (See 10.14, 10.15, and 10.16.) 10.8 Is the stuff sold by Carver really awesome? Some people really like it. Others believe that it doesn't perform up to specifications. Still others believe that it isn't all that it is hyped up to be. One of Carver's claims to fame is lots of watts per pound of weight. As with almost everything else, the best policy is to listen for yourself and see what you think. 10.9 What is a preamplifier? A preamplifier is an amplifying electronic circuit which can be connected to a low output level device such as a phono cartridge or a microphone, and produce a larger electrical voltage at a lower impedance, with the correct frequency response. Phono cartridges need both amplification and frequency response equalization. Microphones only need amplification. In most audio applications, the term 'preamplifier' is actually a misnomer and refers to a device more properly called a 'control amplifier'. Its purpose is to provide features such as input selection, level control, tape loops, and sometimes, a minimal amount of line-stage gain. These units are not preamplifiers in the most technical sense of the word, yet everyone calls them that. 10.10 What is a passive preamplifier? A passive preamplifier is a control unit without any amplification at all. It is a classic oxymoron, because it has no capability to increase the gain of the signal. It is only used with line level sources that need no gain beyond unity. 10.11 Do I need a preamp? Why? The tasks of a preamp are to: Switch between various input signals, Amplify any phono inputs to line level, Adjust the volume, Adjust the treble and bass if necessary, Present the right load impedance for the inputs, and Present a low source impedance for the outputs. If you have a turntable, you NEED a preamp with a phono input. This is because the turntable has an output which is too small for driving amplifiers and because the output of the turntable requires frequency response equalization. You can't connect any other source to a phono input other than a turntable (phono cartridge). Also, you can't connect a phono cartridge or turntable to any input other than a phono input. Microphones also require special preamplifiers. Some microphones also require "phantom power". Phantom power is operating power for the microphone which comes from the preamp. Microphone preamps are often built into tape decks and microphone mixers. If you only have high level inputs, such as the output of a CD player and the output of a tape deck, the main value of a preamp is selecting between inputs and providing a master volume control. If you only listen to CDs, it is plausible to skip the preamp entirely by getting a CD player with variable level outputs and connecting them directly to a power amplifier. Some caveats apply. One, the variable outputs on a CD player are often lower sound quality than fixed outputs. Two, some sources have high or nonlinear output impedances which are not ideal for driving an amplifier directly. Likewise, some amplifiers have an unusually low or nonlinear input impedance such that common sources can't drive the input cleanly. A good preamplifier allows use of such devices without sacrificing sound quality. Unfortunately, the only way to be sure that a preamplifier is of value with your sources and your amplifier is to try one. Almost all receivers contain a phono preamp, a volume control, and input switching. Therefore, if you have a receiver, you may never need a preamp. 10.12 Should I leave equipment on all of the time or turn it on and off? Some gear draws significant electricity, so you will waste money and fossil fuel if you leave it on all of the time. As an example, a common amplifier consumes 40 watts at idle. High-end gear uses far more electricity, but ignoring that, 40 watts x 168 hours x 52 weeks x US $0.0001 per watt hour (rough estimate) is $35/year. Now add a CD player, a preamp, and a tuner, and it really adds up. High-end enthusiasts claim that equipment needs to warm up to sound its best. If you care about the best sound, give your equipment at least 20 minutes to warm up before serious listening. Warm up will allow the inside temperature to stabilize, minimizing offsets, bring bias currents up to their proper values, and bringing gain up to operating level. Either way, good gear will last a very long time. Tubes are known to have a finite life, but good tube designs run tubes very conservatively, giving them life exceeding 10 years of continuous service. Some amplifiers run tubes harder to get more power out, and thereby may be more economical to turn off between use. Filter capacitors will fail after enough time at temperature with voltage applied. They will last longer if turned off between use. However, like tubes, filter caps can last tens of years of continuous use, as can power transformers, semiconductors, and the like. Filter capacitors have a funny problem that justified a simple break-in or reforming when they are restarted after many years of rest. It involves bringing up the power line voltage slowly with a variable transformer. For tips on reforming capacitors, consult "The Radio Amateur's Handbook", by the ARRL. Semiconductors seem to fail more often because of bad surges and abuse than age. Leaving gear off may be best for semiconductors and other surge-sensitive gear if you expect power line surges, as come from an electrical storm or operation of large motors. Fuses seem to age with temperature and get noisy, but they are so inexpensive that it should not bias your decision. However, some are inconvenient to change, and may require opening the case and even voiding the warranty. -- Leo Breebaart -- Moderator rec.music.info Submissions & other mail to: rec-music-info @ cp.tn.tudelft.nl !!! Requests for information do *not* belong in r.m.info! !!! ****************************************************************************** Archive-name: AudioFAQ/part2 Last-modified: 1993/8/19 Version: 1.8 10.13 What about swapping op-amps? Many components use ICs called op amps as audio amplifiers. Earlier op amps had poor sound quality, especially if misused. Some engineers with a strong background in ICs and op amps learned that they could improve sound if they replaced slow, noisy, low slew-rate, or otherwise bad op amps with better ones. Some less informed people tried doing the same thing and made the sound worse. One pitfall with op amp swapping is that some op amps are more prone to unwanted oscillation than others. The faster the op amp, the more likely it will cause an unwanted oscillation, which will really damage the sound. For that reason, Joe may succeed in replacing 741 op amps with 5534 op amps in his gear, and you may fail. It is dependent on design, layout, etc. As technology and design expertise improves, audio op amps get better and swapping is getting less and less useful. Newer op amps are displacing yesterday's best, and sound surprisingly similar to straight wire. Still, there are different op amps for different purposes. Bipolar op amps are ideal for preamplifiers where noise is critical. The OP-27, OP-37, LT1028, and LT1115 are very well received for phono preamps, head amplifiers, and microphone preamplifiers. Bipolar op amps are also more practical for signals with low source impedance. FET devices like the OPA604 and OPA2604 have higher slew rate, higher bandwidth, and lower input current. These op amps are better for line-level inputs and high source-resistance signals. Some amplifiers, like the OP-37 and LT1115 achieve higher bandwidth by using less internal compensation. These amplifiers are not unity gain stable, and should not be used in circuits with low closed loop gain or large feedback capacitors. Some of the better op amps for audio as of today include (* means highly recommended): Single Dual AD847 AD827 AD797* NE5535 NE5534 NE5532 OP-27 AD712 LT1115* LM833 AD811 AD841 AD842 HA5112* OPA2604* LT1057 OP249* LT1028 AD744 With op amp part numbers, there is a lot of room for confusion. Here is a guide to the numbers that is often accurate: Op amp part numbers start with a manufacturer's prefix: Analog Devices uses AD Burr Brown uses OPA Linear Technology uses LT Motorola uses MC National uses LF and LM PMI uses OP Signetics uses NE and SE TI uses TL This can be confused because if TI copies a Signetics op amp, they may assume the Signetics prefix, or they may use their own. Fortunately, if the part numbers are the same, circuitry is almost exactly the same, as is the performance. (Note: almost) The next thing in the part number is two, three, four or five digits. This is invariably the key to the part. If the numbers are the same, the parts are almost surely the same. For example, an LM357N and an LM357J are electrically identical and sound the same. Next is a letter or two indicating the op amp package and possibly how it has been tested and what tests it passed. Unfortunately, manufacturers haven't standardized these letters. Fortunately, you almost never care. If it is a dual-inline (DIP) package and you are replacing a DIP, you shouldn't have to worry whether or not it is ceramic or molded. Likewise, you rarely care if it has 100uV offset or 4mV offset for audio. Finally, you don't care if it wasn't tested at elevated temperatures because you will use it in your house, inside well ventilated gear. So in general, an NE5532J is a TL5532N, and an AD827JN will sound the same as an AD827LD. If you aren't sure about some detail, call or write the IC maker and ask for a data sheet on the parts in question. They will always send data sheets for free, and these data sheets contain details on the various part numbers, internal circuitry, and electrical characteristics. 10.14 Where can I buy electronic parts to make an amplifier? There are many commercial parts distributors that sell only to Corporations. Their prices are often list, their supply is often good, and their service varies. Common ones are Arrow Electronics, Gerber Electronics, Hamilton Avnet, and Schweber Electronics. See your local phone book. There are also distributors that cater to smaller buyers These typically have only one office. Some have lousy selections but great prices. In the following list, (+) means that the dealer has a good reputation, (?) means that the dealer has insufficient reputation, and (X) means that some have reported problems with this dealer. (C) means they have a catalog. All Electronics Corporation (Surplus, Tools, Parts) (?) (C) PO Box 567 Van Nuys CA 90408 USA 800-826-5432 818-904-0524 Allied Electronics (Full Line of Parts) (+) (C) 800-433-5700 Antique Electronics Supply (Tubes, capacitors, etc) (?) 688 First St Tempe AZ 85281 USA 602-894-9503 DigiKey Corporation (Full Line of Parts) (+) (C) 701 Brooks Avenue South PO Box 677 Thief River Falls MN 56701-0677 USA 800-344-4539 Maplin (European Parts) (?) (C) +44 702 554161 (For Orders Only) +44 702-552911 (Customer Service) Marchand Electronics (?) (Crossover kits) 1334 Robin Hood Lane Webster NY 14580 USA 716-872-5578 MCM Electronics (Speakers, A/V Repair Parts, Etc) (+) (C) 650 Congress Park Dr Centerville Ohio 45459-4072 USA 513-434-0031 MesaBoogie (Tubes, instrument speakers) (?) 707-778-8823 Mouser Electronics (Full Line of Parts) (+) (C) PO Box 699 Mansfield TX 76063-0699 USA 800-346-6873 817-483-4422 Newark Electronics (Full Line of Parts) (+) (C) Parts Express (Speakers, Cables, Connectors) (+) (C) 340 East First Street Dayton OH 45402-1257 USA 513-222-0173 Radio Shack (Parts, Low-End Audio) (+) (C) Old Colony Sound (Audio parts and audio kits) (+) (C) PO Box 243 Peterborough NH 03458-0243 USA 603-924-9464 Michael Percy (Connectors, MIT, Wonder Caps, Buf-03) (+) PO Box 526 Inverness CA 94936 USA 415-669-7181 Voice 415-669-7558 FAX Tanner Electronics (Surplus Parts) (+) 214-242-8702 Triode Electronics (Tubes, transformers, boxes) (?) 2010 Roscoe Street Chicago IL 60618 312-871-7459 Welborne Labs (Connectors, Linear Tech ICs, Wima Caps) (?) 6836 South Universtiy Blvd. #70 Littleton CO 80122 USA 303-470-6585 Voice 303-791-7856 FAX 10.15 Where can I buy audio amplifier kits? Alas, Heath is no longer making Heathkits. Alternatives: Audio Synthesis (Many kits from Ben Duncan designs) (?) 99 Lapwind Lane Manchester M20 0UT, UK 061-434-0126 Voice 060-225-8431 FAX Old Colony Sound (+) (See 10.14) Hart Electronics (UK) (?) Hafler (+) Crimson (UK) (?) Mark V Electronics (?) 8019 E Slauson Ave Montebello CA 90640 USA 800-423-3483 213-888-8988 Sage Audio (Various kits UK$95 to UK$430) Construction House Bingley West Yorkshire England BD16 4JH UK 10.16 Where can I read more about building amplifiers, preamps, etc.? Analog Devices Audio/Video Reference Manual Audio Amateur Magazine Audio Amateur Publications PO Box 494 Peterborough NH 03458 USA 603-924-9464 Electronic Music Circuits, by Barry Klein Howard D Sams & Co ISBN 0-672-21833-X Electronics Australia (Magazine with audio projects) AUD47 per year 12 issues, often discounted PO Box 199 Alexandria, Austrailia +612 353 9944 or +612 353 6666 Elektor Electronics (How it works and you-build articles) (no longer published in US. Still available in Europe) PO Box 1414 Dorchester DT2 8YH, UK Enhanced Sound: 22 Electronic Projects for the Audiophile (Some basic projects and some "how it works") by Richard Kaufman Tab Books #3071/McGraw Hill ISBN 0-8306-9317-3 Glass Audio Magazine Audio Amateur Publications PO Box 494 Peterborough NH 03458 USA 603-924-9464 IC Op-Amp Cookbook, Third Edition by Walter G. Jung ISBN 0672-23453-4, Howard W. Sams, Inc. buy from any book store or from: OpAmp Technical Books 213-464-4322 Journal of the Audio Engineering Society (Theory & Experiment) Audio Engineering Society 60 East 42nd Street New York City NY 10165-0075 USA 212-661-2355 Popular Electronics Radio-Electronics Radiotron Designer's Handbook, Fourth Edition (old, tube info) The Technique of Electronic Music, by Thomas H Wells Schirmer Books ISBN 0-02-872830-0 Vacuum Tube Amplifiers, MIT Radiation Lab series Wireless World 10.17 What is Amplifier Class A? What is Class B? What is Class AB? What is Class C? What is Class D? All of these terms refer to the operating characteristics of the output stages of amplifiers. Briefly, Class A amps sound the best, cost the most, and are the least practical. They waste power and return very clean signals. Class AB amps dominate the market and rival the best Class A amps in sound quality. They use less power than Class A, and can be cheaper, smaller, cooler, and lighter. Class D amps are only used for special applications like bass-guitar amps and subwoofer amps. They are even smaller than Class AB amps and more efficient, yet are often limited to under 10kHz (less than full-range audio). Class B & Class C amps aren't used in audio. In the following discussion, we will assume transistor output stages, with one transistor per function. In some amplifiers, the output devices are tubes. Most amps use more than one transistor or tube per function in the output stage to increase the power. Class A refers to an output stage with bias current greater than the maximum output current, so that all output transistors are always conducting current. The biggest advantage of Class A is that it is most linear, ie: has the lowest distortion. The biggest disadvantage of Class A is that it is inefficient, ie: it takes a very large Class A amplifier to deliver 50 watts, and that amplifier uses lots of electricity and gets very hot. Some high-end amplifiers are Class A, but true Class A only accounts for perhaps 10% of the small high-end market and none of the middle or lower-end market. Class B amps have output stages which have zero idle bias current. Typically, a Class B audio amplifier has zero bias current in a very small part of the power cycle, to avoid nonlinearities. Class B amplifiers have a significant advantage over Class A in efficiency because they use almost no electricity with small signals. Class B amplifiers have a major disadvantage: very audible distortion with small signals. This distortion can be so bad that it is objectionable even with large signals. This distortion is called crossover distortion, because it occurs at the point when the output stage crosses between sourcing and sinking current. There are almost no Class B amplifiers on the market today. Class C amplifiers are similar to Class B in that the output stage has zero idle bias current. However, Class C amplifiers have a region of zero idle current which is more than 50% of the total supply voltage. The disadvantages of Class B amplifiers are even more evident in Class C amplifiers, so Class C is likewise not practical for audio amps. Class A amplifiers often consist of a driven transistor connected from output to positive power supply and a constant current transistor connected from output to negative power supply. The signal to the driven transistor modulates the output voltage and the output current. With no input signal, the constant bias current flows directly from the positive supply to the negative supply, resulting in no output current, yet lots of power consumed. Class B amplifiers consist of a driven transistor connected from output to positive power supply and another driven transistor connected from output to negative power supply. The signal drives one transistor on while the other is off, so in a Class B amp, no power is wasted going from the positive supply straight to the negative supply. Class AB amplifiers are almost the same as Class B amplifiers in that they have two driven transistors. However, Class AB amplifiers differ from Class B amplifiers in that they have a small idle current flowing from positive supply to negative supply even when there is no input signal. This idle current slightly increases power consumption, but does not increase it anywhere near as much as Class A. This idle current also corrects almost all of the nonlinearity associated with crossover distortion. These amplifiers are called Class AB rather than Class A because with large signals, they behave like Class B amplifiers, but with small signals, they behave like Class A amplifiers. Most amplifiers on the market are Class AB. Some good amplifiers today use variations on the above themes. For example, some "Class A" amplifiers have both transistors driven, yet also have both transistors always on. A specific example of this kind of amplifier is the "Stasis" (TM) amplifier topology promoted by Threshold, and used in a few different high-end amplifiers. Stasis (TM) amplifiers are indeed Class A, but are not the same as a classic Class A amplifier. Class D amplifiers use pulse modulation techniques to achieve even higher efficiency than Class B amplifiers. As Class B amplifiers used linear regulating transistors to modulate output current and voltage, they could never be more efficient than 50%. Class D amplifiers use transistors that are either on or off, and almost never in-between, so they waste the least amount of power. Obviously, then, Class D amplifiers are more efficient than Class A, Class AB, or Class B. Some Class D amplifiers have >80% efficiency at full power. Class D amplifiers can also have low distortion, although not as good as Class AB or Class A. Class D amplifiers are great for efficiency. However they are awful for other reasons. It is essential that any Class D amp be followed by a passive low-pass filter to remove switching noise. This filter adds phase shift and distortion. It also limits the high frequency performance of the amplifier, such that Class D amplifiers rarely have good treble. The best application today for Class D amplifiers is subwoofers. To make a very good full range Class D amplifier, the switching frequency must be well above 40kHz. Also, the amplifier must be followed by a very good low-pass filter that will remove all of the switching noise without causing power loss, phase-shift, or distortion. Unfortunately, high switching frequency also means significant switching power dissipation. It also means that the chances of radiated noise (which might get into a tuner or phono cartridge) is much higher. 10.18 Why do I hear noise when I turn the volume control? Is it bad? Almost all volume controls are variable resistors. This goes for rotary controls and slide controls. Variable resistors consist of a resistive material like carbon in a strip and a conductive metal spring wiper which moves across the strip as the control is adjusted. The position of the wiper determines the amount of signal coming out of the volume control. Volume controls are quiet from the factory, but will get noisier as they get older. This is in part due to wear and in part due to dirt or fragments of resistive material on the resistive strip. Volume control noise comes as a scratch when the control is turned. This scratch is rarely serious, and most often just an annoyance. However, as the problem gets worse, the sound of your system will degrade. Also, as the problem gets worse, the scratching noise will get louder. The scratching noise has a large high-frequency component, so in the extreme, this noise could potentially damage tweeters, although I have never seen a documented case of tweeter damage due to control noise. Some controls are sealed at the factory, so there is no practical way to get inside and clean out the dirt. Others have access through slots or holes in the case. These open controls are more subject to dirt, but also are cleanable. You can clean an open volume control with a VERY QUICK squirt of lubricating contact cleaner, such as Radio Shack 64-2315. Even better is a non-lubricating cleaner, such as Radio Shack 64-2322. With any cleaner, less is better. Too much will wash the lubricant out of the bearings and gunk up the resistive element. You can also clean some controls by twisting them back and forth vigorously ten times. This technique pushes the dirt out of the way, but is often just a short term fix. This technique is also likely to cause more wear if it is done too often. Try to do it with the power applied, but the speaker disconnected, so that there is some signal on the control. Sealed and worn controls should be replaced rather than cleaned. Critical listeners claim that some controls, such as those made by "Alps" and by "Penny and Giles" sound better than common controls. Regardless of the brand, however, it is essential that whatever control you buy have the same charcteristics as the one you are replacing. For most volume controls, this means that they must have AUDIO TAPER, meaning that they are designed as an audio volume control, and will change the level by a constant number of dB for each degree of rotation. Badly designed circuits will wear out volume controls very quickly. Specifically, no volume control is able to work for a long time if there is significant DC current (or bias current) in the wiper. If the output of the control goes to the input of an amplifier, the amplifier should be AC coupled through a capacitor. If there is a capacitor there, it might be leaky, causing undesirable DC current through the volume control. If you have a circuit with no blocking capacitor or a bad blocking capacitor, you can add/replace the capacitor when you replace the control. However, get some expert advise before modifying. If you add a capacitor to a device which doesn't have one, you will have to make other modifications to insure that the amplifier has a source for its bias current. 11.0 CD Players, CDs, Turntables, and LPs 11.1 What should I listen for when evaluating a turntable or CD player? For tape decks and turntables, beware first of speed variations (wow and flutter). A good check for this is Richard Strauss' "Also Sprach Zarathustra" (aka: The Theme From 2001), which has a long, low, sustained organ note that comes in well before the main theme starts, and is held through the first movement. Concentrate on that. Make sure it doesn't wobble or warble. There's also a good bit at the beginning of Pink Floyd's "The Wall", but it doesn't go on as long, so you've got less time to think about it. Tape decks are prone to losing high-frequency notes, so pick something you like which has lots of treble, and make sure it is clear. The sound of a turntable is largely bound up in the kind of cartridge mounted on it. Make sure to listen to a table with a cartridge similar to what you're buying, and not one in a different price bracket. If possible, audition the turntable with the same arm and cartridge, so that you will experience potential cartridge/arm interactions, too. Most cartridges work better with one arm than another. Treat the tonearm/cartridge pair as a system, rather than independent parts. For CD players, try some piano music. See if the high notes sound tinny. Also, try something which has some soft parts, not the same as turning the volume down. Distortion for CD players (as for other devices) is measured at a high output, but in fact in CD players (unlike others) it's likely to be worse in soft passages of music. Most classical recordings contain a suitable soft passage. Most rock music won't. Distortion in CD players, if you want to call it that, is a function of the granulation noise, or time-delay pre-echo that can come out of the filtering. To listen for this, use material that is rich in high-order harmonics, such as brass music. Unfortunately, you can't reliably predict how a CD player will sound by looking at specifications, features, or the technology it uses. If you want to know how a player will sound, you MUST listen to it. 11.2 Are some discs better than others? Some recordings are better than others. Some artists are better than others. Some recording engineers are better than others. Some microphones are better than others. Some music is better than others. Ignoring the above, there is some difference between discs. Some of the very earliest discs were badly made and deteriorated with time. The technical problems that caused those problems have been solved. Some "gold" discs are available which are advertised to have better life and quality than common "aluminum" discs. These sell for an extra US $15 or more per disc over the cost of the same music on a common disc. Studies have shown that there is an advantage to glass-encased, gold platters for archiving computer data that is not error tolerant and will need to be stored for many tens of years. I have yet to see a similar comparison which justified any extra effort for storing audio recordings for 50 years. Part of the reason for this is that audio recordings contain error correction codes. Another reason is that audio recorders can effectively reconstruct badly damaged audio data, even if there is data completely missing. Some discs seem to have pinholes in the aluminum, which are visible when the disc is held up to a strong light. However, these discs play fine and last very well, so the effect of these pinholes is probably nil. Some have performed studies counting errors on various discs with various players. They found that, in general, the error count was consistent from one player to another. Also, in general, most discs have a low, consistent error rate which is perfectly correctable using the redundant data stored on the disc. This study did find that one group of discs had a higher error rate than all of the rest. This group was the promotional discs, also called "music samplers" given away by music companies to introduce you to their family of artists and performers. Despite these higher error counts, these discs still played fine. If there is no abusive handling involved, I have rarely heard of a disc that degraded with time. Of the few that have existed, they tended to be from one of the bad batches mentioned earlier. There is no doubt that some discs are mastered better than others. Some are badly mixed. Some are so badly recorded that there is noticeable clipping. Some are made from damaged master recordings. CD technology is no guarantee of good music or of a good recording. 11.3 Are CDs better than LPs? Some excellent recordings are mastered digitally, and sound great on LPs. This suggests that there is nothing inherently bad about digital. Some find that LPs sound better than CDs. Advocates of LPs claim that the digital to analog (D/A) converter in home CD players isn't up to the quality of the information on the disc. They also claim that the analog electronics in a home CD player can be poor. Some believe that CDs do not sound like LPs because the CD does not have the frequency response errors, the distortion, or the stereo separation problems of LPs. In general, though, there are good and bad CD players, just as there are good and bad turntables, cartridges, and tone arms. Any ultimate comparison would require ultimate equipment, which is unaffordable. In moderately priced systems, there will be some signal damage from the turntable system and some signal damage from the CD player. LP lovers often learn the nuances of cartridge selection, record care, and even turntable and tonearm adjustment. They have found that the turntable will sound different if the arm height is adjusted, if the cartridge angles are changed, and if the tonearm wire is moved. CDs do not offer as many avenues for the home experimenter. However, Audio Amateur Magazine has published modification projects for CD players; particularly for Magnavox 560 and similar European players. Audio Magazine has also published such articles. 11.4 What turntable should I buy? Despite improvements in motor technology, most great turntables use belt drive. Rubber roller (idler) drive sounds the worst. Select a turntable with a very heavy platter for the least wow and flutter. Give the platter a rap with your knuckle. It should not "ring" like a cymbal. It should feel and sound dead. Also look for a turntable that has good isolation from base to stylus. With the amp on and the turntable selected, but with the turntable motor off, put an old record on the turntable, lower the stylus onto the record, and then tap the edge of the base. Not too hard, you don't want to send the arm flying. At worst, you should hear (through the speakers) a quick 'thump' followed by silence; if you're lucky, you'll hear nothing at all. If the sound continues beyond a quick 'thump', the mechanical isolation is not great, and you might want to look at some other make. To perform this test with some turntables, it will be necessary to unplug the turntable power cord. If the turntable has a tonearm, try to evaluate the arm, too. A good arm should be adjustable in height. A good arm should allow cartridge adjustments. A good arm should accommodate a wide range of cartridges. Despite this, some arms work better with high compliance cartridges, while others are at their best with low compliance. Ask. The original AR Turntable was very well received when it was first made, and the current AR Turntable is still very respected for its price ($450 + arm). Turntables made by Denon, Linn, Rega, Sota, and VPI are also recommended, but can cost more. 11.5 What phono cartridge should I buy for my older turntable? The $30 Grado ZTE+1 is a great value for any home user but a purist. For the purist, there are still many choices, both moving coil and moving magnet. Each sounds slightly different, and has its individual strengths. The Sumiko Blue Point has been recommended at $125 along with the $125 Denon DL-160 and the $150 Shure V15 type V-MR. 11.6 Will phono cartridges still be around ten years from now? Most likely, there will still be cartridges available, but not in the variety available ten years ago. They will become "Special Order" in some stores and unheard of in others. "Pro" or "DJ" cartridges will stay available in good supply, "Audiophile" cartridges will stay available and very expensive, "Mid-line" cartridges will become very scarce, and a few "Budget" cartridges will remain available in copious supply. At the same time, some makers will drop their cartridge lines completely. 11.7 Will LPs still be around ten years from now? There is a strong movement of collectors and purists who will keep their collections and buy good used discs. Count on these people to keep the used disc market hot for 25 years longer. As for new music, less is being pressed today than 20 years ago. Many popular artists are being released on LP in parts of Europe, but availability is dependent on country. One person said that many new LPs are available in Spain. LP sales have increased recently in Japan and in the UK. Polydor is now re-releasing older recordings on vinyl, and will continue to press them as long as it is profitable. Likewise, there are several re-releasing projects in Japan. Some are for Jazz collectors and others are for pure analog as well as classical music lovers. They are selling the LPs by subscription, with shipments every 2 or 3 months. Each release includes about 20 titles. Japan has released over 100 LPs this way last year. 11.8 What about CD green pens? In a nutshell, save your money. A CD player "reads" information on the disc with a laser light beam. Some believe that if you put a green stripe on the very perimeter of the disc, then the light beam will not reflect around inside the disc and will more clearly pick up the data. Scientific studies of the data coming off of the disc have failed to show any difference between a virgin disc and a green painted disc. I have not heard of double blind listening comparisons that have proved that there are people who can hear the difference, although many have performed uncontrolled tests with positive results. 11.9 What about CD stabilizer rings? In a nutshell, save your money. The data coming off of the disc is a serial string of ones and zeros. If this bit stream has jitter, then it may reach the D/A converter out of sync. If this happens, then the actual analog signal recreated will have jitter, and won't be perfectly true. The vendors of stabilizer rings say that using these rings will reduce jitter and make a more perfect signal. Vendors also claim that the rings can increase the mass of a disc, making it spin more smoothly, and reducing transient load on the power supply from the motor. Some players will not play discs that have stabilizer rings on them. The clamp can't handle the thickness. Other players play ringed discs, but do not play them well, because the disc motor was not built for the added load. With those exceptions, scientific studies of the data coming off of the disc have failed to show any improvement going from a virgin to a ringed disc. I have not heard of double blind comparisons that prove that people hear the difference, either. 11.10 What about CD spray treatments (ArmorAll et al)? In a nutshell, save your money. Current wisdom is to avoid any disc coating or spray. Some will definitely damage the disc. There are many theories on what ArmorAll can do to a disc. One is that it reduces static which will attract the delicate head of the laser detector to the disc. Another theory is that the cleaner will fill voids in the disc with silicone, thereby making it easier to read by reducing diffraction effects. Scientific studies of the data coming off of the disc have failed to show any difference between a virgin disc and a treated disc. I have not heard of double blind listening comparisons that have proved that there are people who can hear the difference. One of the strongest proponents of ArmorAll issued a "recall" on his advice. He now warns that ArmorAll can damage the disc. He also advises that you can clean ArmorAll off treated discs with Dawn dish detergent. 11.11 Are 1-bit CD players better than multi-bit players? In a nutshell, they are virtually the same. There are some excellent sounding 1-bit players and some excellent sounding multi-bit players. Some feel that the 1-bit technology has more future because it can be improved with the rapidly improving digital technology, while the multi-bit players improve with slowly improving analog technology. Multi-bit also has its advocates. All of the various D/A converters try to do the same thing, and try to achieve the exact same ideal performance. How well they succeed is more a function of their skill and the quality of the parts that they buy than the technique that they use. In other words, the architecture of a D/A converter is less important than the quality of its implementation. 11.12 Are three lasers better than one in CD players? Some players have one beam, some three. All use one laser diode to generate the beam. Three-beam is just a different method for doing track alignment. Neither is better than the other. There are good 1-beam players and good 3-beam players. Manufacturers want advertising claims and "More Beams Is Better" sounded good to some marketing people. Trust your ears. 11.13 Is the BMG 8-for-1 deal good? Yes. You have to put up with their frequent mailings. You can elect the "POSITIVE OPTION" and not have to answer each mailing to avoid an order. You should expect to pay approximately $2.00 per disc for shipping and handling in the US and more elsewhere, but even at that price and assuming that you will buy one of their discs for $16.00, you still do well. Assuming, of course, that you want at least eight of the discs that they are offering for sale. Some states requires sales tax on BMG sales, and some states tax "free" discs, but the tax still is small compared to the discount from retail. The BMG collection contains over 2500 discs. This includes classical, pop, jazz, and other. All BMG discs come from the larger labels. Some rumored that BMG discs are inferior to the discs sold in normal retail chains. This has not been substantiated. In fact, BMG distributes their discs through retail chains, as well as through the mail, so you may get a BMG disc either way. If you are interested in learning what is available from BMG, there is a fairly current list of the BMG offerings available by ftp at "cisco.nosc.mil". After logging on, give the command "get [.cd]bmg.txt". (Note: Type what's in the quotes. Don't type the quotes.) This list is NOT perfect, may have errors, may have some omissions, and may have some obsolete discs in it, but is the best total compendium easily available. The list is maintained by neidorff@uicc.com (Bob Neidorff) and the archive is maintained by mike@jammin.nosc.mil (Mike Pawka). 11.14 What should I do if there is a problem dealing with BMG? The number to reach BMG is 317-542-0414. Their people have been very cooperative with me and others. It is always good policy to confirm any phone call with a letter, restating the problem and the resolution you were promised over the phone. It is good practice to write down the name of the person you speak with. If BMG sends you something that you didn't order, DON'T OPEN THE PACKAGE. Write REFUSED on the package and put it back in the mailbox. They will accept the return and credit your account for any charges. 11.15 How do I get out of the BMG racket? If you have taken any discs from BMG, you must either return what you have ordered or fulfill the terms of your original agreement. This often means buying one disc at full price and paying for the shipping on all discs you ordered and received. Once you have done this, you can quit the club at any time. Take your next order form and mark it with a bold marker in large letters "CANCEL MEMBERSHIP" and mail it to: BMG COMPACT DISC CLUB, PO BOX 91413, INDIANAPOLIS, IN 46291 USA. It may take a month to fully take effect, but they will honor your request. While waiting for the cancel order to take effect, be sure to return all future order forms marked the same way. Otherwise, you may wind up with unwanted discs. 11.16 How do I get the most out of BMG? Only buy one disc at full price, fulfilling your obligation. Request the "POSITIVE OPTION" so that you save on postage. Only buy from special fliers. Every month, except November and December, they send out a "Two for half price then one free" flier. They have almost all of the stuff in the regular fliers. They even offer "Buy one get two free" sometimes. Wait for those special deals. You can even order discs from an October catalog using the order form that came in the February catalog. You can get even more out of BMG by signing up, getting 8 discs for the price of one, quitting, signing up again, etc. People have done this successfully. BMG reserves the right to deny membership to anyone, so you run a very slight risk of being denied membership the 20th time. However, I have never heard of anyone ever being denied membership for any reason. 11.17 What is a 1-bit (Mash, Bitstream) D/A converter (CD player). 11.18 What is the best under-$200 CD player? Once, Magnavox (and the identical Philips) CD players were known for poor reliability. They are much better today. Some believe that for sound, an under-$200 Magnavox is as good as any in its price range. Be sure to listen for yourself before you buy. 11.19 What is the best under-$500 CD player? Some recommend the Rotel 855 and 955. 11.20 What's wrong with the CD longbox? Some CDs are sold shrink wrapped in a square plastic storage box known as the "jewel" box. This is the ideal packaging for CDs. It has almost no unusable components and adequately protects and displays the disc. The shrink also implies that the disc is new and unopened, but shrink can never assure a new disc. Some CDs are still sold in a cardboard box that is more than 2X the size of the jewel box. This "long box" is ecologically wasteful and useless. It rarely contains additional information about the disc or the artists. Its primary purpose is to discourage theft in retail stores, but it is even poor at that. These boxes are BAD. Some stores use a reusable plastic long box. When you buy a disc in one of these boxes, you take the disc and jewel box with you and leave the plastic long box with the cashier for reuse. Not perfect, but a good compromise. 11.21 How can I promote better CD packaging? Vote with your money. Don't buy CDs packaged in the long box. If you go to a store and they have CDs in the long box, tell the owner that you never buy CDs in the long box. Then find stores which don't use the disposable long box. People have been doing this over the past few years and have made a difference in many stores. (The fact that the long box costs more than simple shrink wrap has also helped the cause.) 11.22 How can I clean a dirty CD? Use a drop of dish detergent and lots of clean water. Do not rub. Never rub or wipe in a circle. Rinse the disc in running clear water, shake off most remaining drops, and lightly pat dry with a soft, clean cloth. 11.23 Can you repair a damaged CD? If the disc is lightly scratched on the bottom, then you can polish out the scratch and probably repair the disc perfectly. If there are lots of scratches or deep scratches, or there is damage on the top, you may be facing a lost cause. The music information is immediately under the label. If you scratched the reflective layer, the disc is normally unrecoverable. Before trying any repair, try washing the disc with clear water and a bit of liquid dish detergent. Do not scrub or rub hard. Rinse the disc with clear water and shake off as much water as you can. Finally, wipe the last few drops off with a soft, clean cloth, in a radial direction. SMALL scratches can be removed with a scrufty T-shirt and toothpaste, such as Tom's Toothpaste. You may wish to try a thin coating of Johnson's Klear floor wax on the bottom of the CD. Often it will cover the scratches enough to allow playing. The refractive index is pretty close to polycarbonate, so filled scratches will be nearly invisible. Noteworthy Music (800-648-7972) sells CD repair kits (#CDR 200, $11.99, one shipping unit). They seem to work as advertised, although getting the disc to the point where you can't see any sign of the scratch does take real care and persistence. You can buy professional plastic polishing compounds at many hobby shops. The ones used for polishing acrylics, plexiglas, etc. work. Ordinary lapidary jeweler's polishes also work. You'll need a rough polish to remove the scratches, then tin oxide to polish to a mirror finish. Telescope lens kits also work. Finally, T-Cut, a car paintwork polish, works well for big scratches. 11.24 Can I add digital output to a non-digital-out CD player? Some Magnavox CD players using the Philips chip set can be modified. Look for a SAA7220 IC. If it has one, then it can be modified. If you have experience modifying electronic equipment, follow this procedure: Take pin 14 of the SAA7220 IC and remove whatever terminating resistor is on it. Connect it through a 560 ohm resistor to the input of a wide band pulse transformer. Tie the other end of the primary of the transformer to ground. Pulse Engineering PE65612, Schott Corp 6712540, and Scientific Conversions SC916-01 all will work. Bypass the primary through a 620 ohm resistor. Connect the output of the transformer to an RCA jack. Do not ground either side of the RCA jack. This output is now S/PDIF compatible. (Thanks for the tip to Positive Feedback) 11.25 What can I get in the way of a CD test disc? Many use the Hi-Fi News & Record Review test discs. So far, these have received only positive comments. Chesky produces 2 test discs. The first, "Chesky Jazz Sampler Volume I" contains some excellent imaging test signals (called LEDR), some well-recorded acoustic jazz, and other test signals. The second, "Chesky Jazz Sampler Volume II" has similar music & different tests. Stereophile produces two test discs. The first seems of limited value. The second just came out. Denon also produces two test discs. The first, "Digital Audio Check" is more useful for home use. The second, "Audio Technical" is more for repair shops and test-disc addicts. | If you are looking for test CDs, one source of supply that | stocks lots of different test CDs is: | DB Systems | Main Street | Box 460 | Rindge Center NH 03461 USA | 603-899-5121 11.26 How do the letters ADD on my CD relate to sound quality? The simple answer to this question is that there is no relation between the three letter code and sound quality. Those three letters refer to the recording and mastering tools used in making the CD. The first letter refers to the recording process. For example, a disc labeled ADD was ANALOG recorded, where a disc labeled DDD was DIGITALLY recorded. Analog recording means that some form of conventional analog tape recorder was used, whether it be a two-track home-quality recorder or a very expensive wide-tape, high-speed, multi-track recorder. Digital recording could be as simple as a two-track DAT recorder, or can be a much fancier multi-track digital recorder. | The second letter refers to the mixing and editing process. | Mixing and editing is the process of combining a multi-track | master recording, setting levels, editing out defects, | adjusting equalization, and creating a two-track final tape. | This can be done with a digital signal processors, and it can | also be done with analog signal processors. There are good | machines available for this which are analog and good machines | which are digital. | | The third letter refers to the final mastering, which for a CD always a digital product. I have seen discs that are labelled as AAD, ADD, DAD, and DDD. Future releases may not have this three letter code on them because they don't tell you anything that is significant. Also, some codes have been used incorrectly on some discs, which makes the information that much more meaningless. 11.27 How can I clean LPs? There are expensive machines for this purpose which work very well. One popular model goes by the name Nitty Gritty. These machines spray cleaner onto the record, work it into the grooves, and then vacuum the cleaner and dirt out. If you are serious about records and have lots of them, it may be a good investment for you. If you have a more reasonable collection, you might be happy with a good hand washing every now and then. To give your records a good hand washing, start by preparing this wash: 1 gallon distilled water 90 ml 70% isopropyl alcohol 1 gram Alconox (a laboratory detergent) Also, get a natural bristle brush and trim it to the correct stiffness/bristle length so that the bristles can get into the grooves but aren't stiff enough to scratch the record. Lay the LP flat and pour a thin coat of the above fluid on it. Brush the wash into the grooves with the bristle brush. Brush in the direction of the grooves, going through all grooves. Flush the wash and dirt off with cool, running tap water. Rinse the record with distilled water and pat it dry with a soft, clean cotton cloth. 11.28 How do you set the stylus pressure correctly? Stylus tracking force is typically adjusted at the back of the tonearm with a knob that is calibrated in grams at the stylus tip. With the control set to zero, the stylus should sort-of float above the record surface. The control is then increased to the number recommended by the cartridge manufacturer. Do not, under any circumstances, use a lower than recommended force, as the cartridge may lose the ability to maintain contact with the groove wall on passages of large amplitude. This WILL result in RECORD DAMAGE. If you want the best possible tracking and sound quality, you will want to fine-tune the tracking force. Use a test record and listen very carefully, or get the help of a good dealer with a battery of instruments. 11.29 How do you set the anti-skating on a tonearm? If you have a recommendation or suggestion from the tonearm manufacturer, follow their advice first. They will give you the best starting point. Some tonearms come with calibrated anti-skate. The manufacturer of these tonearms has tried to calibrate the anti-skate control so that if you match the setting of the anti-skate to the setting of the stylus pressure, you will have nearly perfect anti-skate. Read the manufacturer's recommendations to see if this applies to your tonearm. You can see gross errors in anti-skate by looking at the stylus. If you shine a light on the front of the tonearm while playing a record, you will be able to see whether the stylus is centered in the stylus holder. If the stylus is biased to one side or another while playing a record, then the anti-skate is way off. More subtle adjustments can be made by listening for mistracking. If you can, obtain a record with equal left right modulation at high frequency with ascending modulation magnitude (volume), such as the Shure ERA-III, IV, or V test record. They have five bands of "greensleeves" played on flute, and you fiddle until the audible breakup is equal in both channels, and adjust tracking weight until it occurs in the highest band. This is, like other cartridge and tonearm adjustments, easier for the experienced hand than the beginner. Some high-end dealers have electronic instruments which allow them to accurately adjust anti-skate and other cartridge and tonearm parameters. If you can get this service, consider yourself fortunate. 11.30 How else do you adjust a tonearm/cartridge/stylus? There are a few other critical adjustments. Again, a good high-end dealer may be your best resource. Your ear may also be your best test instrument. You need a level turntable. Use a quality carpenter's level. Some people like the Shure stylus force gage for setting stylus pressure accurately. Other tools which are well recommended are the Geo-disk, a good protractor, and above all, the Cart-Align, which uses a very precise etched plastic mirror for cantilever alignment. You'll also want to set the tracking angle. It CAN be done by eyeball, but is best done with test instrumentation and a record. There is also the cartridge angle, tonearm height, etc. Read the instructions which came with your tonearm for the best specific advice for that tonearm. Tonearm cable is more critical than any cable anywhere else in the signal chain. Cable capacitance directly sets the high frequency characteristics of the cartridge. In addition, the correct grounding of the shield is essential to minimize hum. It may be necessary to change preamp input capacitors so that the cable/preamp combination loads the cartridge with the right overall capacitance. Replacing tonearm cable will have a similar effect, but may be harder to change tonearm cable than to change preamp input capacitors. Consult the cartridge, tonearm, and preamp manuals for specific advice. Also refer to 16.6 for more information on tonearm cable. An excellent article on setting up a turntable is: Stereophile, July 1990, Pages 62-85. 11.31 Do CDs deteriorate with time? What is their life span? A CD consists of a polycarbonate top layer, an aluminum (or gold) metal reflective layer, a polycarbonate bottom layer, and some miscellaneous printing ink. Of these materials, polycarbonate seems to be extremely stable with time provided that it is well cared for. Do not use any liquids on a CD that contain silicones or solvents. Do not leave CDs in sunlight or other bright light. Do not stick labels on CDs. Do not write on CDs. Do not expose CDs to temperatures higher than normal room temperatures. Don't leave a CD under water. Even the top side of a CD is critical and subject to damage. Some pressings from the early 1980s used ink which damaged the polycarbonate top layer and eventually got into the aluminum. These inks are not in use today. Some earlier discs were made with imperfect sealing around the perimeter of the disc. This was evident because the aluminum in the disc extended all of the way to the disc edge. These discs were known to fail due to moisture getting to the aluminum and causing it to oxidize. Modern CD factories have solved this problem as well. With those cautions, modern CDs will last for more than 30 years without deterioration. Most of the CDs which were made in 1983 are still around today and still sound good. 12.12 Should I buy "xxx"? Which is better: "yyy" or "zzz"? We can provide facts and opinions (and you get to decide which is which :-), but we can't recommend if, or which way, you should jump, because we don't know what your priorities are. (That won't stop us from trying, though!) For example, if you are considering a used item at a low price vs. a new one at a higher price, one of us might say "go for the new one because of the warranty", when another would say that you can fix it yourself if it breaks. They're both right. This also applies to speakers. One may have very good, flat bass, but only go so low, where the other may go lower, but have less flat frequency response. Which is better? Depends on the buyer. Good speakers are carefully designed to achieve a balance of performance that matches the priorities of the designer. Some designers put much of their budget into appearance. Some designers put their budget into very high efficiency. Others strive for the smallest box which can deliver an acceptable low frequency performance. Do you really want people on the network making that decision for you? 13.0 Listening Rooms and Houses 13.1 How should I place speakers in my room? What size room is best? You are after two important, distinct goals: flat frequency response and good three-dimensional image. At your disposal is the room size, the room shape, speaker height, speaker placement, listening position, and room treatments. Even though good speakers are essential to good sound, room effects are also extremely important. In many cases, the differences in room effects will be more noticeable than spending twice as much on speakers! For smoothest bass response, a listening room should be as large as possible, have dimensions as unrelated as possible, and should be optimally damped. Although nothing is ever ideal, there are a few room dimension ratios that are better for listening rooms: Height Width Length 1 1.14 1.39 1 1.28 1.54 1 1.6 2.33 If your room isn't shaped like that, don't worry. These effects are not major. Also for smooth bass response, woofers should be at distances from the nearest three room boundaries that are as different as possible. In some cases, the line dividing the listening room into left and right halves must be considered a room boundary. Also, for smooth bass response, the listener's ears should be at distances from the nearest three room boundaries that are as different as possible. All of this is essential because a wall near a speaker boosts the bass from that speaker at some frequencies. If a speaker is the same distance from three walls, then some frequencies will be emphasized much more than others, rather than slightly more. For best three-dimensional image, a listening room should have good symmetry about the plane between the two speakers. This means that if one speaker is in a corner, the other speaker must be in a corner. If this symmetry is not right, the first reflection from the wall behind one speaker will be different from the first reflection from the wall behind the other speaker and critical parts of the stereo signal will be damaged. Also, no large object should block the path from speakers to listener or from speaker to speaker. Speakers should be elevated so that tweeters are at listener ear height. The distance between speakers should be no greater than the distance from each speaker to the listener. Finally, the tweeters should be aimed at the listeners. A normal box-shaped listening room with bare walls will have "slap echo" which will reduce intelligibility. A good cure is randomly-placed wall hangings consisting of small rugs spaced an inch or so away from the wall to increase sound absorption. Another cure is convex-shaped art objects on the walls to disperse harmful reflections. If money is available, commercial room treatments such as "Tube Traps" and "RPG Diffusers" are also valuable, but many of the benefits of these exotic devices are available with simpler techniques. As a general rule, in a good room, speakers and listener can be close to room boundaries with minimal adverse effects. In a bad room, a good strategy is to place both speakers and listener as far away from room boundaries as possible. An excellent starting point for speaker placement is to measure the listening room diagonal dimensions. Divide that measurement by three. Put each speaker that distance from a corner, on the room diagonals. I-----------------------------------I I I I L I I I I S S I I I I-----------------------------------I Place your listening position midway between the two speakers and approximately half way from the speakers to the wall. Be sure that there is nothing in the "triangle" formed by the listening position and the speakers. Try this and then move things 12" (30cm) at a time to see if you can improve the sound. Your ears will be a better guide than any commonly-available instruments. To keep track of what you are doing, take notes. To remember exactly where you put the speaker on the floor, a practical trick is to mark the floor with a sewing needle and thread. 13.2 How do I wire a house for sound? A fundamental principle of physics is that the farther a signal travels, the more the signal will be degraded. Translate this to mean that the shorter the wire, the better. Understanding this, the idea of running speaker cable between every room of the house isn't as attractive as it first seems. If you still decide to wire your house for sound, you should do it at the same time you're wiring for telephone and electricity. It is possible to wire a house after the walls are closed, but it becomes very difficult. It is economical to use common house wire (Romex, UF, NM, etc) for speaker wire in the walls, but this may violate building codes. Check with an electrician or inspector first. It will also confuse future electricians, so label the wire clearly, all along its length. If you want to make your house like a recording studio, it is best to use the techniques of recording studios. When studios run long lengths of sound cable from one room to another, they drive the cable with 600 ohm line amplifiers. They also use shielded, twisted-pair cable. They only connect the shield at one end of the cable. Finally, they use balanced inputs at the other end of the cable. 13.3 Where can I read more about listening room construction and tuning? "Building a Recording Studio" by Jeff Cooper Mix Bookshelf "Handbook for Sound Engineers" "The Master Handbook of Acoustics" by F Alton Everest "Sound Engineering 2nd Edition" by Don and Carolyn Davis; Howard W. Sams & Co. (C) 1990 "Good Sound" by Laura Dearborn Introductory, but clear and accurate "Sound Recording Handbook" by John M. Woram Howard W. Sams & Co. #22583 Excellent General Reference "Audio Technology Fundamentals" by Alan A. Cohen Howard W. Sams & Co. #22678 Overview of Audio Theory "Introduction to Professional Recording Techniques" by Bruce Bartlett Howard W. Sams & Co. #22574 "Modern Recording Techniques" by Hubar and Runstein Howard W. Sams & Co. #22682 "Sound Studio Production Techniques" by Dennis N. Nardantonio Tab Books 14.0 Recording There are more different recording systems available today than ever before. Digital and analog are both available to the consumer. With the advent of consumer digital recorders, used pro analog recorders are becoming available for surprisingly low prices. Now may be the time for you to buy a microphone and recorder and make your first! 14.1 What is DAT? What is its status today? DAT (Digital Audio Tape) is currently the standard professional digital format for 2-track digital recording. DAT had a short-lived consumer presence, but never "made it". As digital recorders have no tolerance for clipping, using a DAT recorder takes a slightly different knack. The results can be worth it, however, as DAT format offers the same resolution and dynamic range as CDs. DATs record for up to 2 hours on a tape, and can run at three different sampling rates: 32 kHz, 44.1 kHz (for CD), and 48 kHz (the DAT standard). 14.2 What is DCC? What is its status today? DCC is Philips' attempt to modernize the regular cassette. DCC decks can play analog cassettes, and can record new Digital Compact Cassettes. They use stationary heads (DATs use rotary heads as do VCR's), and although they are digital, they use lossy compression to fit all the data on the cassette. Although DCC sound quality is far better than the 1960 standard cassette, the DCC does not have the sound quality present in DAT or CD. DCC may be a good choice for consumers who want to assemble mix tapes for cars or walkmans, but is not suitable for any professional applications. As of December 1992, DCC is very new, DCC equipment is very expensive, and the ultimate future of DCC is not assured. 14.3 What about writable compact discs? What is the status today? Recordable CD's are available, but are very expensive. Blank discs sell for approximately $35 each, and the recorders start at around $6,000. These units are mostly used by recording studios and other audio professionals. 14.4 What is the best cassette deck under $200? 14.5 What is the best cassette deck under $400? 14.6 What is PASC? Can I hear the effects? PASC (Perceptual Audio Sub-band Coding) is a data-compression algorithm. It increases the length of recording that can be stored in a given number of data bits by eliminating sounds that the developers' research claims can not be perceived by human listeners. Its most important component is the omission of quiet sounds that occur at the same time and near the frequency of louder sounds. It provides up to a 4x increase in the length of recordings a given digital medium can hold; this is essential to allow full-length digital recordings on DCC (and on MD, which uses a different compression technique). It is not necessary to translate CD data to analog before compressing it using PASC, nor the reverse, but today's DCC decks do not have digital inputs or outputs. You CAN hear PASC, but it is very difficult, since it is not a distinctive noise (like a hiss) nor a consistent diminution (like a notch in a speaker's response), but a broad, uncorrelated dropout in a changing collection of sounds that are masked by sounds that you can hear very easily. Since it is lossy, repeated PASC recording will cause progressive loss, and this signal damage may become easily noticeable. This is a side effect that recording companies hope will have the effect of discouraging piracy via DCC. 14.7 What is SCMS? Can I hear the effects? SCMS (Serial Copy Management System) is a copy-protection system intended to stop rampant piracy of commercial recordings to digital tape. SCMS allows the home taper to copy from a CD to a digital tape, but prevents anyone from digitally copying that new digital tape. You CANNOT hear SCMS. 14.8 How can I bypass SCMS? There are professional devices used by engineers to manipulate the digital bitstream, but they cost several hundred dollars and are not cost effective for consumers. If you need to make perfect digital copies of digital copies, buy a professional digital recorder. Pro models do not have SCMS, are more durable than consumer recorders, and may have better quality electronics than consumer models. 14.9 What's this about a tax on DAT? Every digital audio tape recorder and every blank digital tape sold in the USA is priced to include a "premium" or "tax". This tax is collected by the US Copyright Office and distributed to the recording artists and record companies that own the copyrights to commercial music. These fees are supposed to repay them for lost royalties. Many believe that this "tax" is illegal, because it represents an assumption that the buyer will use the recorder and tape to violate a copyright, and not to record their own works. A founding principle of the USA legal system is that everyone is assumed innocent until proven guilty. If you believe that this law is unjust, write your elected representatives. 14.10 Is it legal to copy an LP, CD, or pre-recorded tape? In the US today, it may be legal to copy LP's, CD's, etc. for your own private use (such as to copy a CD to play on your walkman). UK law specifically prohibits this, but it is almost never enforced. It is definitely not legal in the US, UK, or almost anywhere else, to copy these sources for commercial purposes, or to give the copies to others. It is as of yet unclear whether you own the rights to sell or give away a copy of a recording if you made the copy on media which was sold with an included digital audio tax. 14.11 How do I clean and demagnetize tape heads? First, a caution: DAT recorder tape heads are VERY fragile. Before cleaning the heads on a DAT recorder, get specific recommendations from a very knowledgeable source that is intimately familiar with DAT head cleaning. In the internet, a good source is the DAT-Heads-Digest FAQ. For more information on DAT-Heads-Digest, see section 20.2, below. To clean tape heads, use pure isopropyl alcohol and lint-free swabs. Wipe the metal parts of the transport with alcohol (DON'T wipe the rollers!) and allow them to dry. Throw the swab away after use. Be exceedingly careful when cleaning the heads on a DAT. DAT heads are notoriously easy to misalign by incorrect cleaning. Practical tape head demagnetizers are available for under $10. Try to find one with a plastic coated tip. If you can't find one which is plastic coated. you can slip a drinking straw or plastic tube over the tip for the same effect. This plastic will prevent the demagnetizer from scratching the head. Before plugging in the demagnetizer, remove all tapes from your working area and unplug the recorder. Hold the demagnetizer away from the recorder as you plug it in. Slowly bring the tip of the demagnetizer up to the tape head and slide it back and forth across each tape head for five one-second strokes. Then pull it away from the head slowly and go on to the next. After demagnetizing the heads, use the tip on each metal tape guide with a similar five strokes. Last, slowly pull the demagnetizer far away from the recorder and unplug it. Recording engineers use a demagnetizer before each recording session. 14.12 How do I adjust a tape recorder for best results? Adjusting a tape machine for best results usually requires special equipment and test tapes. Unless you know what you're doing, leave it for a pro. If you are serious about doing it, buy the service manual for your particular tape recorder. It will list a detailed procedure, as well as describe the correct test tape and tools. As for setting of record levels, it is best to experiment with different levels on different tape brands. Different formulation will reach saturation for different levels. Generally speaking, the transients on a Chrome tape should peak at about +6 dB above 0, though some formulations can take significantly hotter signals. 14.13 Where can I get new pinch rollers or drive belts? Projector-Recorder Belt Company Whitewater WI USA 800-558-9572 14.14 What is a good rubber (pinch) roller cleaner? Teac RC-1 available from J&R Music World 59-50 Queens-Midtown Expressway Maspeth NY 11378-9896 USA 800-221-8180 or 718-417-3737 Tascam Rubber Cleaner RC-2 available from: Tape Warehouse Chamblee GA 1-404-458-1679 14.15 How can I program a recorder to tape a radio broadcast? Radio Shack and Panasonic make a clock/radio/cassette that can be set to record at a specific time. Radio Shack also sells 120 minute cassettes, which can be used for 60 minutes per side. The recorders are not high quality, and the long tapes are fragile, but it works. You can buy "appliance timers" at hardware stores that will start and stop an appliance at a specific time. Radio Shack sells fancier versions of the same thing for more money. Gadget freaks love "X-10" control systems. These can be configured to do the same thing. All require a recorder that can be left in RECORD mode. Such recorders are identified by a "TIMER" switch on the front panel. Many cassette decks have a TIMER switch for use with timers. Memorex sells a "CP-8 Universal Remote" with a built-in timer. Available for approximately $90.00 from either: Crutchfield 1 Crutchfield Park Charlottesville VA 22906 USA 800-955-3000 or 804-973-1811 or J&R Music World 59-50 Queens-Midtown Expressway Maspeth NY 11378-9896 USA 800-221-8180 or 718-417-3737 This can be set to start a recorder at a particular time. As the recorder will be started from a remote control rather than by the power line voltage, no timer switch is required. Radio Shack has a very similar product available for $99.95, may be less on sale. Damark also sells a learning remote with a built in on/off timer and sleep timer. It can learn 17 commands per device on a total of 5 devices and should be great for taping a few shows. They also sell a 8 device remote with timer. As Damark sells close-outs, these items may not be available in the future. Damark 7101 Winnetka Avenue North PO Box 29900 Minneapolis MN 55429-0900 USA 800-729-9000 or 612-531-0066 Use a VCR for audio-only recording. Hook the audio in to the output of a radio, tuner, or receiver. You may also have to connect some video signal to the VCR so that the sync circuits work correctly. 14.16 Will CrO2 or Metal tapes damage a deck made for normal tape? No. They will work fine. They are no more abrasive than common tape and may actually be less abrasive than very cheap tapes. Recorders which are designed for CrO2 or Metal tape have different bias settings and equalization settings to take best advantage of the greater headroom and to give flat response with these different types of tape. However, they use similar if not identical heads as less expensive tape recorders. Almost all tapes are in some way lubricated, and these lubricants minimize wear and squeaking. 14.17 Why do my old tapes squeak in my car cassette deck? One problem that will cause this is "binder ooze". The binder is the glue which holds the oxide particles to the backing. With time, this binder can ooze forward and actually get past the oxide particles, so that there is sticky stuff on the surface of the tape. When this sticky stuff goes past the heads, it can cause a slight stick, which will sound like a squeak. You won't feel it with your fingers, but it is there. If you have a prized tape with this problem, consider baking the tape in a home oven at a very low temperature, like 150F. This might cure the problem by drying out the binder. 14.18 Is VHS Hi-Fi sound perfect? Is Beta Hi-Fi sound perfect? The HiFi recording format is subject to two different problems: Head-switching noise and compression errors. To get perfect reproduction, the FM subcarrier waveform being played back by one audio head must perfectly match the waveform from the other head at the point of head switching if a glitch is to be avoided. If you record and then play the tape on the same VCR under exactly the same conditions, you have a reasonable chance of this working. But if the tape stretches just a bit, or you play it on another VCR whose heads are not in exactly the same position, or the tracking is off, the waveforms will no longer match exactly, and you will get a glitch in the recovered waveform every time the heads switch. This sounds like a 60 Hz buzz in the audio, which is often audible through headphones even if not through speakers. The same glitch will occur in the video waveform too, but since head switching always happens during vertical retrace, you won't see it. The wonderful signal to noise ratio of VHS HiFi is achieved through the use of compression before recording and expansion after playback. The actual signal to noise ratio of the tape itself is about 35 dB and a 2.5:1 compressor is used to "squeeze" things to fit. Like all companders, this produces audible errors at certain places on certain signals, such as noise "tails" immediately after the end of particularly loud passages. Worse, compressors often have problems simply getting levels right. That is, if you record a series of tones, starting at -90 dB and working up in 1 dB increments to 0 dB, and then play them back, you will almost invariably have level errors. The trend from soft to loud will be there but the steps won't be accurate. Two or three of your tones might come out at essentially the same level, then the next one takes a big jump to catch up or even overshoot. For music, the result will be that the relative levels of some instruments, passages, etc. will not be accurate. This doesn't matter as much for movies, which tend to have steady volume level. Also, movie enjoyment is rarely hurt by these level errors. VHS and Beta HiFi is fine for reproduction of movie and tv soundtracks. They are also perfectly fine for non-critical audio applications. But VHS and Beta HiFi are not serious competitors to DAT, CD, open-reel analog tape, or even a high quality cassette deck. 14.19 How do HiFi VCRs compare to cassette recorders? DAT recorders? VHS HiFi and Beta HiFi are analog recording formats which use modulation techniques to record a video signal and a stereo audio signal on a videocassette. The audio capabilities typically surpass that of the "linear" audio tracks found on all video recorders, thus the "HiFi" designation. "HiFi" is essential for getting good sound quality on your video recordings and out of pre-recorded videos. HiFi is also touted as an excellent audio recorder for audio-only (no picture) applications. On paper, the specifications are typically superior to analog cassette but inferior to DAT. In reality, the quality of HiFi video recorders is better than low quality cassette recorders but not as good as high quality cassette recorders when they are used with noise reduction systems. In no case can a HiFi video recorder compare to DAT. It suffers from generational loss and audible noise. Many people use VHS HiFi for recording radio broadcasts, since VCRs often have built-in timers and can record for up to 9 hours. If you use a HiFi video recorder to record from an audio-only source, beware that some decks will not function properly without a video signal for synchronization. If you are interested in very good quality sound, use a deck with manual level control. 14.20 What is the difference between VHS HiFi and Beta HiFi? VHS HiFi uses "depth modulation"; Beta HiFi uses "frequency modulation". 14.21 Is there any good reason to buy a HiFi VCR for common TV shows? If you do not own a stereo TV, the purchase of a HiFi VCR will give you the capability to listen to stereo TV broadcasts to your system. 14.22 What is the best cassette tape? One simple answer to this question is that the best tape is the tape which was used to align your tape recorder. A second simple answer is that more expensive tapes are frequently better in terms of quality of the backing, durability of the oxide, accuracy of the shell and guides, and life. Background: When you make a tape recorder, you build electronic circuits which have specific, non-flat frequency response. These circuits correct for the non-flat response of the tape heads, the recording process, and the tape. These circuits can be adjusted after the recorder is made, but adjustment is tricky, and may or may not be successful with every tape made. The designer of the tape recorder picked one tape as their standard when they did the design, and built that recorder to work well with that particular tape. It may work better with a different tape, but it won't necessarily sound the best with what one person calls the best sounding tape. From a review of frequently given answers to this question, it is obvious that almost every brand of tape has its advocates. Many brands also have their detractors. Maxell and TDK tend to have a strong following, but that is in part because they own a large share of the US tape distribution market. 14.23 What is the best Reel-to-Reel tape? See 14.22. Just as cassette tape recorders are set up specifically for one type of tape, reel-to-reel tape recorders are equalized and biased so that they are best with one specific brand and model of tape. Just as more expensive cassette tapes will last longer and have less noise than cheaper ones, you can expect fewer dropouts, better quality control, and lower noise from more expensive reel-to-reel tapes. The major brands in reel-to-reel tape include Ampex, Scotch (3M), AGFA/BASF, and Maxell. 14.24 What is Type I, Type II, Type III, and Type IV cassette tape? 15.0 Mail Order Mail order is appealing. The general hope is that by using mail order, you avoid pushy sales people, you pay fixed, discounted prices, and you have written catalog descriptions to help you select your purchase. In practice, most mail order today is "phone order", in that the company completes the deal with a phone call. Many of the "mail order" companies don't even have price lists or catalogs. They are just retailers that are willing to sell over the phone and ship the merchandise to you. In some cases, retail store sales are better deals than mail order. Don't expect the lowest price from the first place you call. Also, don't expect excellent service from everyone, and especially not from the company with the lowest price. 15.1 Who sells brand XXX equipment mail-order? Consult the frequent rec.audio mail-order survey published by nau@SSESCO.com (William R. Nau) or contact William Nau directly. This survey is also available via FTP in the pub/rec.audio directory of SSESCO.com. If you have any mail order experiences to share, please send them directly to William Nau. 15.2 Is the stuff sold by DAK really awesome? Damark? DAK buys in large quantities. They buy what they think they can sell. They buy close-outs as well as new first-line merchandise. They honestly represent their merchandise with specifications. They offer more information on their product, if possible, on the phone through their toll free number. I know of many people who have bought from DAK and been happy. I personally have bought from DAK and been happy. Regarding Damark, opinions of people on the net are similar. The products are as described, they deliver what they say they will, and will take back or replace unsatisfactory merchandise. I have not heard any unsatisfied Damark customers. On the other side, the catalog writers at DAK use some very flowery language which is intended to lead you to believe that they are selling gold for copper prices. In this sense, the words in their catalog may be deceptive. The DAK people have a good sense of "what the market will bear". They price their products to sell, but not to give away money. Mail order prices tend to be 10% to 20% less than discount, which is 10% to 20% less than retail. DAK has to compete with other mail order dealers, such as Damark, but they send out SO MANY CATALOGS that they really don't have to cut prices too far to sell. DAK has recently gone through hard financial times. This puts buyers in some slight risk, because if they go out of business, you may get easy warranty service on their products. I say easy because most DAK products are covered by a manufacturer's warranty, and you can often get service from the manufacturer as well as from DAK. I believe that DAK is over their slump, but I am not sure. For more on warranties, see 19.1, below. 15.3 Is the stuff sold by Cambridge Sound Works really awesome? 15.4 What should I watch out for when buying mail order? Many of the cautions mentioned in warranties (19.1) apply. Look for a store which has been around a long time. Look for friends which have dealt with the store and been satisfied. Look for a store which does not lie or stretch the truth. 15.5 What is gray market? See warranties (19.1), below. 15.6 Are there any good mail-order sources for recordings? Noteworthy has a good reputation among net readers as a supplier of CDs. They have a range of discs available centered firmly on the mainstream, and are reasonable in price. Shipping is $3.75 for 1-5 CDs. They offer over 14,000 different CD titles. Their offerings are all from US labels. They give a free catalog and also have modem software and catalog on floppy discs for $9.95. Noteworthy Music, Inc 17 Airport Road Nashua NH 03063 USA 800-648-7972 Voice 603-881-5729 Voice 603-883-9220 FAX BMG and Columbia also sell CDs mail-order, but have a smaller list of offerings and higher prices. However, BMG and Columbia have interesting deals to entice new customers. Read the fine print before you sign to be sure that they are right for you. BMG and Columbia both have promotional offerings to "members" which allow you to buy two or three discs for the price of one. These can be very good deals, if you want what they have. Look at their advertisements in common magazines and Sunday newspapers for a better idea of what they carry. They list much of their line in their ad. Don't expect much more. Bose Express also sells CDs. Their reputation so far is very knowledgeable people, a large collection, and high prices. Their catalog costs $6.00. Bose Express Music The Mountain Framingham MA 01701 USA 800-451-2673 or 508-879-1916 Ext. 2008 Tower Records has a mail order department which also sells CDs. Their classical catalog costs $13.45. Their other catalog costs $10.45. Tower is a large retail chain. Many have bought from their retail outlets happily, but no one has expressed any comments on their mail order service yet. Contact: Tower Records Mail Order Department 692 Broadway New York City, NY 10012 USA 800-648-4844 or 800-522-5445 Another source is Music New Hampshire; 800-234-8458. They sell many $3.79 post-paid sampler CDs and also many independent label single-artist discs. Most single artist discs are $15.00 each. Shipping is $3 for 1-3 discs and $5 for 4-up. Their stuff is mostly obscure artists. They have Rock, Jazz, Classical, Folk, Country, and Children's offerings. Affiliated with CD Review. Music New Hampshire - Wayne Green Inc 70 Route 202N Peterborough NH 03458-1107 USA If you like the idea of buying CDs by Modem, consider The Compact Disc Connection 1016 East El Camino #322 Sunnyvale CA 94087 USA Voice 408-733-0801 Modem 212-532-4045 New York City NY 312-477-3518 Chicago IL 408-730-9015 Sunnyvale CA They have a collection of over 58,000 CD titles. People have said that their service is excellent. Prices are fairly good. Shipping is $3.50 for orders under $100.00 and free for larger orders. They do not stock anything, but deliver from the warehouses of their suppliers. This means that some items may be back ordered or completely discontinued while remaining in their on-line data base. They advertise 94.2% of orders in 1992 shipped, though not necessarily immediately. If you have a modem and enjoy browsing a data base, their data base is a a very enjoyable experience. However, the phone bill can be quite prohibitive to those calling from out-of-town. There have been a couple of music (cd/lp) mail-order lists compiled on the net - one older list can be found via anonymous ftp to ftp.uwp.edu in the file: /pub/music/misc.mailorder.rmm Someone is revising this file and it should be updated or found in a new file name there in the future. Another list contains vendors that specialize in progressive rock, electronic and experimental music, is maintained by Malcolm Humes and posted sporadically to alt.music.progressive, rec.music.misc, & rec.music.info. This also can be ftp'd from ft.uwp.edu, in the file: /pub/music/misc/mailorder.progressive Federal Music and Video markets "Discount Coupon Books" featuring two-for-one CDs and Tape deals. They require payment with the order, which many consider risky. One company that distributes these coupon books for Federal Music is Reed Music. The price from Federal or Reed Music with the two-for-one deal is comparable to the price from Noteworthy. So far, no net user has yet related any positive or negative experience with Reed Music or Federal Music and Video. Federal Music and Video has been in business since 1985, so is probably legit. However, in that they require payment in advance it is probably safer to avoid them completely and use a discounter like Noteworthy. When considering mail purchases of CDs, consider shipping costs. It is common for people to charge between $1 and $3 per disk for "shipping and handling". This makes mail order less attractive, but may be equally balanced by a lack of sales tax. -- Leo Breebaart -- Moderator rec.music.info Submissions & other mail to: rec-music-info @ cp.tn.tudelft.nl !!! Requests for information do *not* belong in r.m.info! !!! ****************************************************************************** Archive-name: AudioFAQ/part4 Last-modified: 1993/9/1 Version: 1.8 16.0 Wire More than any other topic, speaker cables and equipment interconnects seem to use up rec.audio bandwidth echoing the same theoretical arguments, testimonials, and opinions. Controversy can be stimulating, educational, and also amusing. Please try to keep postings aimed at one of those three goals, and avoid the insults and emotion. Also, try to avoid echoing a common position or principle, as described below. 16.1 Do speaker cables matter? To avoid confusion and repetition, here is some terminology. Cables are connectors attached to wires. Wires generally have multiple conductors optionally surrounded by a shield and outer insulating covering. Cables can introduce noise into the signal, act as a filter (and thus change the frequency response of the system), and provide nonlinearities from improper (intermittent/loose) connections to or between the connectors. It is quite scientifically conceivable that some cables do cause a difference in sound, because of the differences in DC resistance, interconductor capacitance, and connector attachment alone. The effects of exotic conductor weaving and materials are not so well established. In general, these effects (once we eliminate DC resistance), seem to be small. However, if your system is at least fairly good, then some folks have observed (although not in an experimental, double-blind sense) significant differences in system performance with different cables. The effects are said to be quite system specific; the only real guideline is to try them and see which ones seem to sound better in your system. Roughly speaking, the price ranges for speaker cables is low (under $1/ft), medium (under $6-8/ft), and high (up to $100/ft and more). Try to arrange it so you can trial such cables; at several hundred dollars per set, experiments can be expensive. In any system or experiment, it is essential that the differences between cables be separated from the differences between connectors. You should have an EXTREMELY solid connection between cable and speaker. Speakers operate at very low impedances, so that bad connections will create significant artifacts or signal losses at any power level. For example, if the connection has a linear resistance of just 1 ohm, the speaker damping factor will be dramatically reduced, making bass muddy. If the connection contains imperfect metal oxides, then a slightly rectifying junction will block the signal, producing compression, distortion, and other non-linear effects. 16.2 What speaker cables are available and how good are they? There is a wide range of speaker wire available, ranging from 30ga zip cord (~$.10/ft) to exotic wires costing over $300/ft. The material used ranges from copper to oxygen-free copper (OFC) to silver. (There are a bunch of others as well.) Oxygen-free copper is probably NOT any different from common copper in sound. If you hear a difference between two cables, it is not a difference between oxygen-free and common copper. Resistance may be significant for speaker cables. The higher the resistance, the more the cable will affect the sound, all else equal. The resistance characteristic of metals is called resistivity. The resistivity of copper is 1.7 microohm-cm. Silver is very slightly lower, 1.6. Gold is a bit higher, 2.4. Silver and gold are different from copper in other ways than resistivity. Gold does not oxidize in normal environments, so gold contacts will not need periodic cleaning and will not create rectifying junctions. Silver will oxidize, but the oxide of silver is conductive, so oxidized silver will still make good contact. Copper oxide is a bad conductor. Oxidized copper contacts may insulate, may conduct, or may rectify. Copper is a bad material for cable terminals, but this may or may not mean anything for the conductor itself. 16.3 What can I use for budget speaker cables? First, a few words on terminology. Wire is sized by AWG or BS gauge number. Larger numbers represent smaller wire. AWG 40 (also called 40 gauge) is as fine as human hair. AWG 12 is 2mm or .081" diameter. Some wire is classified as solid, because it contains one strand per conductor. Other wire is called stranded, because it consists of many strands per conductor. Stranded wire is far more flexible than solid wire. Most wire is made from drawn copper. Some wire is sold that is claimed to be made with a process that produces oxygen-free copper. Oxygen-free copper has a different metallurgical structure than common copper and may or may not conduct current better. Some critical listeners have reported excellent sound from large diameter solid copper wire, such as home wiring "Romex 12-2". At least one expert has said that common 18-gauge solid copper hook-up wire sold by Radio Shack also works very well. Also recommended on a budget is Sound King wire, a 12 gauge oxygen free copper stranded cable. This is available from MCM Electronics for $.39/ft. The scientific literature indicates that small gauge wire generally sounds worse than large gauge. Resistance-related effects of the cable can be eliminated by using at least 12 gauge wire, particularly for long runs. Of course, shorter runs are always preferred, because they come much closer to the ideal zero-length wire, with no resistance, no capacitance, no inductance, and no change in signal. 16.4 What can I use for budget speaker connectors? The worst connectors are push-down, or spring terminals. Screw terminals with solid copper wire are much better. Gold-plated binding posts and gold spade lugs are inexpensive by audiophile standards and are extremely stable. Binding posts with spade lugs can be tightened to get a very good mechanical joint, and may offer the lowest electrical resistance of any connector. Gold plated banana plugs and jacks are very good speaker terminals. Good ones are more expensive than gold spade lugs, however, they also provide a bigger area of contact, and are more convenient when you must frequently reconfigure the system. Banana plugs should be periodically monitored for corrosion and loss of spring tension. Monster offers a banana-plug connector with an expanding center pin that forms an even better connection than common gold banana plugs. At approximately $25 per pair, the Monster banana plugs aren't a budget connector. All else equal, connectors with gold surfaces are better than connectors with any other surface. This is for two reasons. First, gold is extremely inert, meaning that unless gold is exposed to very harsh chemicals or harsh vapors, it will not corrode or oxidize. It will remain a pure, low-resistance conductor. Second, gold is quite soft, so that if a gold-plated connector is squeezed between two metal surfaces, it will deform slightly to fill scratches and voids, giving a very broad, low-resistance contact area. Corrosion of connectors is often a problem. Gold-plated terminals and connectors somewhat avoid this problem; problems with other connectors can be mitigated by unplugging and replugging the connector on a regular basis, cleaning the contact areas with a pencil eraser, or by using a contact enhancer such as Cramolin or Tweek. When you use a contact enhancer, be very sure to follow the directions, and avoid spreading enhancer about your equipment. 16.5 What about interconnects, such as the cable between tuner and amp? Line-level interconnects conduct smaller signals than speaker cables; the typical signal ranges from -2V to +2V (the CD output standard) with currents in the microamps (the corresponding values for speaker cables attached to a largish power amp might be -70V to +70V and currents of many amps). Line-level interconnects can be divided into single-ended (or unbalanced), and balanced interconnects. Home audio is almost always single-ended interconnects. Single-ended interconnects almost always use a form of the RCA connector (or phono plug). RCA plugs form fair to poor connections that degrade with time as corrosion works into the metal-metal contact and as the spring tension of the connectors relax. Gold-plating reduces the effect of corrosion and locking RCA connectors solve most of the mechanical problems. However, these premium phono connectors are rare and expensive. For example, a gold-plated Vampire locking RCA plug costs approximately $23/pair. If RCA connectors weren't a de facto standard, we'd recommend against them. Unbalanced interconnect wires vary in geometry, material and price. Cheaper wires have a single conductor (normally stranded) and a shield and cost $.20-$2/ft. Medium (complexity and price) wires have two conductors (often arranged as a twisted pair) surrounded by a shield and cost from about $3-$20/ft. Exotic wires have all sorts of geometries and materials (such as stranded silver conductors, or ribbon cable braided around a core, or in one extreme case, a tube filled with mercury!). Prices may be as high as $200-$300/ft. Balanced interconnects have three conductors: two for the signal one for ground, and additionally a shield. The standard connector for balanced cable is the ITT/Cannon XLR connector, which is quite good mechanically (they lock). Equivalent connectors are also available from Switchcraft, Neutrik, and other vendors. If you have to run cables longer than 12 feet or 4 meters, the greater noise immunity of balanced interconnects is often a good idea. For this reason, balanced connectors are standard equipment in professional installations such as studios, public address systems, and broadcast stations. There is not much variation in balanced cables. The three brands mentioned above are known to be rugged, high quality and moderately priced. Slightly weaker imported connectors are available, but they aren't dramatically cheaper. For most systems, the most important aspect of a cable are the mechanical reliability of the connectors; in particular, the joint between connector and wire, and the joint between connector and socket. Typically, interconnect cables are short. It is worth getting just the right length; cables often come in .5 meter increments. With quite good systems, some people observe differences in sound between various interconnects. This is quite system-specific and the same advice as given above applies: try several brands. Most good dealers will loan interconnects for home evaluation. In cables where the shield does not carry the signal or ground, the shield is normally only connected to ground at one end. In systems where there are significant differences between ground levels on various components, it may make a difference which way such cables are connected. Typically, the end where the shield is grounded should be at the source of the signal. Often, such cable has arrows on it pointing in the direction of the signal flow. In any case, try both orientations. There are many objective reasons why cables might cause differences in sound by interacting with the drivers in the signal sources as well as by providing non-linear effects in the RCA connector. Most of these effects are again related to interconductor capacitance and resistance, and the quality of the shielding provided by the "shield" conductor. In balanced cables the quality of the "twisted pair" inside the shield is also important. One might note that a shield protects from only capacitively coupled interference, and not from any magnetic field interference. The twisted pair in a balanced line provide some magnetic rejection, as does steel conduit. However, steel conduit has other characteristics which make it undesirable for audio in general. 16.6 What about Phono Interconnects: Phono interconnects are part of the link between a cartridge on a turntable and a preamp (or head amp or receiver). They are a special case of line-level interconnects because the signal is much lower, typically 1 to 50 millivolts. They are also intended to operate into a higher impedance, typically 47K ohms, and form part of the capacitive load for the cartridge. The low signal levels mean that the shielding of the cable, and the presence of a separate drain/shield are more important, as is a good ground. A separate solid ground should come along with the cable as a separate lead co-routed with the cable. In addition, the low signal levels make a good solid connection to and through the connectors MUCH more important, because of the greater sensitivity to low-level nonlinearities. Wire capacitance is often ignored in line-level interconnects; however, in a phono interconnect, it may constitute half of the total capacitive load of the cartridge. Obviously, then, two cables with significantly different capacitances should sound differently. In this sense, the "right" cable for one cartridge may be too low or high in capacitance for another cartridge. For low-impedance cartridges (most moving coil cartridges), the wire must have low resistance to prevent cartridge unloading and frequency-dependent signal loss. In addition, as the signal levels are quite low, shielding is important. Unfortunately, copper shields do not block stray magnetic fields, so in the case of phono cables, careful routing may be even more effective at reducing hum than special wire. 16.7 Is there really a difference in digital interconnects? There are now three kinds of digital interconnects that connect transports to D/A converters: coax, plastic fiber (Toslink) and glass fiber (AT&T ST). In theory, these should sound EXACTLY the same (bits are bits). However, this assumes good circuit design (in particular, the clock recovery circuits of the DAC, and careful consideration of electronic noise) which may be compromised because of cost considerations or ignorance. Note: different signaling schemes are used on plastic and glass fiber. In any case, some people claim to hear a difference; of those who do, most seem to prefer the glass fiber. However, the technology of fast digital data transmission in consumer electronics is evolving very quickly now. Any specific recommendation should be treated with suspicion until the industry matures. 16.8 Can I make very good interconnects myself? Yes. You will need to be the judge of whether or not they are as good as $100 interconnects, but it is easy to make interconnects that are better than the $2.00 set which comes with new equipment. There are two necessary ingredients: two-conductor shielded cable and RCA connectors. There is a lot of debate over what is the best cable, but in general, the lower the capacitance per foot, the better. Choice of insulation is harder. There may be an advantage to polypropylene or teflon over polyester or rubber, but even that is debatable. If you are buying wire from an electronics distributor, some have successfully used Belden 1192A microphone cable. It is rubber insulated, so very flexible. Another recommended cable is Belden 8451. This is a polypropylene cable with foil shield. Finally, consider Belden 89182. This is foamed teflon insulated, so very low capacitance, and foil shielded. If you plan to make a long cable, this low capacitance cable may be the best choice. There is also a variety of RCA connectors available. A good connector would be gold plated and machined to tight tolerances. A poorer connector will not fit as well, will make poorer contact as the connecting surface oxides, and will lose its springiness with use. When wiring the cable to the connector, use one wire for signal, (the tip of the RCA connector) and one wire for ground (the shell or outer conductor of the RCA connector). Some cables use a foil shield which is difficult to solder. These cables typically have a drain wire parallel to the foil which can be used for soldering. Others use a braided shield. Regardless of which type of wire you have, connect the shield or the shield drain wire to ground on only ONE SIDE. This will stop noise picked up by the shield from causing ground noise. It can be a touchy job soldering RCA connectors. Before you use your new cables, check with an ohmmeter or a continuity tester to make sure that you have not accidentally sorted the signal and ground leads together, either with a stray drop of solder or a loose wire strand. 17.0 The Press 17.1 Which magazine should I read? Which ever one you like. None are absolutely objective. Here's a list of some common ones: Audio Amateur ($20/yr 4 issues) (Do-it-yourself) Box 576 Peterborough NH 03458 USA 603-924-9464 Audio Critic (US $24/yr 4 issues) (High-end) PO Box 978 Quakertown PA 18951 USA 215-538-9555 or 215-536-8884 Audio Magazine (US $24/year 12 issues. Mid-fi) Subscription Office: PO Box 53548 Boulder CO 80321-2548 USA 800-274-8808, 303-447-9330 Editorial Office: 1633 Broadway New York, NY 10019 212-767-6000 Audio Observatory (US $15/year 12 issues) 22029 Parthenia Street West Hills, California 91304 Audiophile (High-end, High-$$$ Buying Guide, Blind reviews) Haymarket Trade & Leisure Publications Ltd 38-42 Hampton Road Teddington, Middlesex, TW11 0JE, UK +44 81 943 5000 US Inquiries should go to: Eric Walter Associates Box 188 Berkeley Hts NJ 07922 USA 201-665-7811 Audiophile Voice 2001 Palmer Ave Suite 201 Larchmont, NY 10538-2420 USA Bound For Sound (US $18/yr 12 issues) (High-end) 220 North Main St Kewanee IL 61443 USA 309-852-3022 Car Audio and Electronics ($19.95/year 12 issues) Avcom Publishing Ltd 21700 Oxnard Street Suite 1600 Woodland Hills CA 91367 USA 818-593-3900 CD Review (Music Reviews; all tastes, only CDs.) $19.97 per year 12 issues PO Box 588 Mount Morris IL 61054 USA Glass Audio ($20/yr 4 issues) (Do-it-yourself, tubes) Box 576 Peterborough NH 03458 USA 603-924-9464 Hi-Fi Choice (Mid-end. Comparative reviews with graphs, tables, and subjective commentary; 'Buying Guide' section) Dennis Publishing Ltd. 14 Rathbone Place London, W1P 1DE, UK +44 71 631 1433 Hi-Fi News and Record Review (Mid-end. Good new record reviews) Subscriptions Department Link House Magazines Ltd 1st Floor Stephenson House, Brunel Centre Bletchley, Milton Keynes MK2 2EW, UK Hi-Fi World (Friendly, lower-mid-end magazine) (reviews and "how things work" articles) Audio Publishing Ltd 64 Castellain Rd Maida Vale London W9 1EX, UK +44 71 266 0461 In Terms Of Music (Emphasizes music reviews, new) PO Box 268590 Chicago, IL 60626 USA 312-262-5918 International Audio Review (US $38/yr, 12 issues?) 2449 Dwight Way; Box 4271 Berkeley CA 94704 USA Positive Feedback (US $25/yr 6 issues) (high-end) Oregon Triode Society 4106 N.E. Glisan Portland OR 97232 USA 503-235-9068 Sound Practices (US $16/yr 4 issues) (Do-it-yourself) Box 19032 Alexandria VA 22320 703-836-4382 Speaker Builder ($25/yr 6 issues) (Speaker projects) Box 576 Peterborough NH 03458 USA 603-924-9464 Stereophile (US $35/yr 12 issues) (High-end) 208 Delgado Santa Fe NM 87501 USA 800-238-2626 or 505-982-2366 Stereo Review (US $6.97/yr 12 issues. Lower end/mass market) Subscription Office: PO Box 52033 Boulder CO 80323-2033 USA Editorial Office: 1633 Broadway New York, NY 10019 212-767-6000 The Absolute Sound (US $46/yr 8 issues) (High-end) Subscription Center: Box 6547 Syracuse NY 13217 USA 800-825-0061 Editorial Office: 2 Glen Avenue Sea Cliff, NY 11579 516-676-2830 The $ensible Sound (US $20/yr 4 issues) (Mid/High-end) 403 Darwin Drive Snyder NY 14226 USA 716-681-3513 or 716-839-2199 What Hi-Fi (Mid-end; comparative, subjective reviews) (contains it's own buyer's guide with recommendations) Haymarket Trade & Leisure Publications Ltd 38-42 Hampton Road Teddington, Middlesex, TW11 0JE, UK +44 81 943 5000 US Enquiries should go to: Eric Walter Associates Box 188 Berkeley Heights NJ 07922 USA 201-665-7811 17.2 Which reviews are better? Some reviews are so colorful and exciting, that they make great journalism and fun reading. Lets ignore these for now, even though they have their place. Beware of reviews from magazines that advertise the same product. The likelihood of bias is too high. Unfortunately, that rules out 99% of the reviews in magazines. Stereo Review has a bad reputation for loving everything made by every advertiser. Even high-end journals such as Stereophile and The Absolute Sound can be influenced. A classic example of misleading reviews occurs with equipment submitted to a magazine for review. The manufacturer may send the editors a carefully built, adjusted piece for review. The magazine will honestly rave about it. The manufacturer will then send the design off-shore for more economical manufacture and assembly, and the quality will suffer. Lower quality components will be substituted for prime parts. Adjustments will be made to wider tolerances or will not be made at all. The design may be completely changed to make it more manufacturable. You will unknowingly get a completely different piece than reviewed. Home auditions with one or two candidates from each of a few dealers are your best guide to be sure that you get what you want and pay for. 17.3 Is Consumer Reports right? Consumer Reports is the most objective testing lab we have ever found. Unfortunately, they are also the world's least specialized testing lab. They market their testing to the average consumer. The average consumer will not hear some of the subtle differences which audiophiles hear. For that reason, Consumer Reports ignores issues that others feel vital. Consumer Reports also insists on basing their audio testing predominantly on lab measurements. Although lab measurements do tell many differences between devices, interpreting lab measurements for best sound is difficult or impossible. For example, it is very hard to compare two speaker frequency response curves and tell which will sound better. Some $3000 speaker frequency response curves look worse than some $600 speaker curves, even when tested in the same setup. On the other side of the issue, Consumer Reports has improved its test methods, and will continue to improve. Expect the accuracy of their reviews to improve with time. The Consumer Reports frequency-of-repair data base is larger than any similar data base published and can be trusted as well as any statistic. 18.0 Retail 18.1 Should I use an up-scale retail store? This is probably the best place to listen to gear in a controlled environment, next to your home. This is the best place to find expensive, high quality gear. This is the place which is most likely to have a good policy on home trials and a liberal return/upgrade policy. This is also likely to be the most expensive place to shop. One exception to this is that these stores have the ability to sell demos, returns, and discontinued gear at very advantageous prices. Some up-scale dealers will negotiate price on large systems or expensive purchases. It never hurts to ask. There are definitely better and worse local hi-fi stores. If you find a really good one, it is probably worth the extra money to buy from them, rather than from discounters. A really good store will not push you to buy what they want to sell. A really good store will allow you to take your time with your decision. A really good store will not distort the truth in describing equipment. A really good store will help you get the most out of your purchase by showing you how to set it up. They will tell you what placement works best for the speakers. (Don't believe them if they tell you to put them anywhere.) A really good store also selects their lines carefully. They don't want dissatisfied customers or warranty returns any more than you do. A really good store will also have technical equipment and/or skilled technical people that can perform tricky adjustments correctly, such as cartridge and tonearm alignment. Due to the nature of the customer, a hi-fi store in a shopping mall is likely to use high-pressure sales techniques. They know that the majority of their customers are distracted easily by 299 other stores. Most of their sales go to customers that come in for 3 minutes, select something, and leave. There are exceptions to this, of course, but if there was a good generalization, it would be to look elsewhere. There are stores in large buildings, small buildings, private homes, shopping plazas, and every other conceivable venue. Search from among these to find one that meets your needs and fits your style. 18.2 Should I use a discount store? If you need to listen carefully before making up your mind, discount stores can be very frustrating. If you know exactly what you want, then this can be a great place to save money. Don't expect knowledgeable sales help or after-sale support. Be sure to ask about the warranty (see 19.1 below on warranties). 18.3 Is it right to negotiate price? Most people feel that it is fair to negotiate. Some feel that it is fair to lie in negotiating, as the sales people frequently lie to you also. Others think that lying to get a lower price is an immoral practice. It may even be illegal, an act of fraud. Some people feel that if you negotiate over price, you encourage stores to mark prices artificially high, so that the stores have room to negotiate. Others feel that in negotiating, you are asking the store to accept a lower profit, or asking the sales person to take a lower commission and are directly hurting them. 18.4 How can I negotiate price effectively? A great source of information on this topic is available from books on buying a new or used car. However, some very helpful general tips include: Know the competition and the dealer. Know the gear. Know the prices available elsewhere. Believe in your research, not their words. Stand your ground. Be nice to the people but hard on the deal. Be prepared to walk away if they won't agree. Expect their lines and prepare responses in advance. For example, expect the dealer to claim that the Nakamichi deck is the best cassette deck on the market. Be ready with a reply such as at that price, you can buy a DAT machine which has better frequency response, lower signal to noise ratio, etc. 18.5 It sounded great in the store. Is it great? Never let anyone else pick stereo for you. Especially not speakers. They all sound different, and you don't need a golden ear to hear the differences. Listen for yourself and ignore what the sales people say. If you are still unsure, ask the sales people to let you take the gear home for a home trial in exchange for a large deposit. Home auditioning takes 99% of the risk out of store auditions. 18.6 Do sales people try to trick the customer? Some do and some don't. Some will treat unpleasant customers badly and treat friendly people well. Most sales people aren't wealthy. They sell stereo to make a living. If they can sell you a more expensive piece of equipment or a piece of equipment with a higher profit, they will make more money. Usually, this figures into everything they say. Some sales people claim to be altruistic. Some sales people really are open and honest. They may starve with this approach, or they may have a nice enough personality, a good enough product line, a good enough store behind them, or enough technical background to overcome this "limitation". 18.7 How can sales people trick the customer? Often, a customer will trick him or herself without help. We are often swayed by appearance, sales literature, position of the equipment in the show room, and our own desire to buy what others will like. Some times, the sales person will actively try to push a particular piece of equipment by demonstrating it against another piece of equipment which is inferior or defective. Some sales people will demonstrate a set of speakers while simultaneously driving a subwoofer, even though they are not telling you this. With the subwoofer, it probably will sound better. Some sales people will demonstrate one set of speakers louder than others. Louder almost always sounds better. Most stereo buyers go into the store, spend a few minutes selecting what they want, lay down big bucks, and leave. They don't need to be tricked. They don't listen carefully. They trust the sales person's choice as best in their price range. For non-technical reasons, these people are the most likely to be satisfied with their purchase. 18.8 What should I ask the sales person? What do you want to know? Seriously, the best questions are those which the sales person can answer without distorting the truth. Don't ask a sales person to compare their brand to a brand they don't sell. Don't ask "how good is the ...". Ask questions of fact. Here are some questions you may want to ask: If I don't like it can I return it for a full refund? Can I try this out at my home in exchange for a deposit? What does the warranty cover? For how long? What do I need to know to set this up for best sound? Do I get a manufacturer's warranty with this? Where do I take this to get it repaired under warranty? Where do I take this to get it repaired out of warranty? 18.9 How do I impress the sales person? Why would you want to? You have money and he doesn't. 18.10 How do I get the best service from a sales person? Be honest with the sales person. Set some reasonable request and ask them to meet it. For example, say that you will buy this if you can try it at home first and listen to it side-by-side with a piece from another store. Alternately, say that you saw the same thing at store Z for $xx less, but you will buy it from the guy if he will match the price. 19.0 Miscellaneous 19.1 What do I need to know about warranties? Warranties have a few basic components. The first is the term of the warranty. The second is what is covered. The third is who supports the warranty. The fourth is what restrictions. Term is fairly self evident. What is covered is more detailed. In audio electronics, typically everything is covered with a "parts and labor" warranty. Often mechanical components such as tape heads are covered by different terms, such as shorter terms on labor and longer terms on parts. Likewise, speaker warranties vary widely, from unconditional with no term limit to a basic 30 days parts and labor. Some warranties come from the manufacturer. Others come from the dealer. Still other warranty support is available with certain premium charge cards. A common restriction on some warranties is that the equipment is not covered unless it is sold by an authorized dealer. A few dealers have lied about being authorized dealers. Equipment sold by an unauthorized dealer is almost always sold completely legally. This unauthorized dealer may, in fact, be fully authorized to sell, but not authorized to sell manufacturer's warranties. In buying gear this way, dealers can get it cheaper, and provide the service themselves. This kind of gear, with a full warranty from the dealer is referred to as gray market equipment. Manufacturers discourage buying from these gray market dealers, but the risks are fairly low. If the dealer is local and well established, the risks are minimal. If you buy equipment mail-order, a dealer warranty may be a pain in the neck, especially if you have to ship the gear to the dealer more than once to get it fixed correctly. Then again, some factory service requires shipping gear far away at your expense, too. Frequently, home audio equipment is sold with a warranty restriction that if the gear is used commercially or in any profit-making enterprise, then the warranty is void. This is to protect the manufacturer from having to frequently repair equipment meant for light service. Professional audio equipment often comes with very liberal warranty terms, such as lifetime parts and labor. Professional gear takes heavy use and severe wear from constant transportation. It is expected to be able to take this abuse. All gear, electronic and mechanical, is known to have three principal failure modes: abuse, infant failure, and end-of-life failure. In addition, a few of the failures occur at random. Infant failure occurs in the first fifty hours of use, and is the principal responsibility of warranties. Infant failure is frequently caused by defective parts or a design defect. Abuse failure is that caused by a person who pulls a cable too hard, bangs the equipment on the table, pushes the controls too firmly or too fast, or does anything else which the manufacturer did not expect. These are the gray areas of warranties. They do not represent a manufacturing defect in the manufacturer's eyes, but they do leave you with a broken device. To get the best chance of coverage against this kind of failure, select a brand or a dealer with a very liberal warranty policy. End-of-life failures are rarely covered by warranty. Tape heads have a finite, calculable life, as do rubber rollers, speakers, cables, batteries, bearings, and motors. The life of some of these components can be extended by intelligent care. For example, the life of common rechargeable batteries can be extended by good recharging practice. Likewise, some cleaners can dry out rubber, and will lead to premature failure. Don't expect warranty support for any of these problems, and if you get it, feel lucky. 19.2 What is blind testing? Non-blind? Double-blind? If you want to compare pieces of equipment, recordings, or people, you could run an experiment. You could select an experimenter to initiate various trials, select some subjects to listen to the sounds, and then ask the subjects questions about what they hear. However, if you want meaningful results, it is necessary to set up the experiment correctly, and ask the right questions. One of the major problems with any experiment is that the subjects may become aware of the experimenter's hypothesis and allow this awareness to influence their behavior. One technique for preventing such bias is to keep the person who conducts the experiment unaware of the hypothesis of the research. Unfortunately, experimenters invariably form SOME hypothesis of what's going on, and these hypotheses affect how they deal with subjects. A more reasonable solution involves allowing the experimenters to know the true hypothesis but somehow keeping them ignorant of the specific experimental condition of each subject. This is known as a Partial Blind Experimenter technique. An example of this is that the person running an experiment knows that the main experimenter wants to determine which connecting cables are best at signal carrying, but would not know which cables are being used at any given time during the experiment. It is also important for subjects not to become aware of the experimenter's specific hypothesis. Subjects often become highly responsive to any cues, intended or unintended, in the research situation that suggest what they are supposed to do to appear normal or "to make the study come out right." This problem can be present in judgment experiments, particularly those in which each subject is exposed to more than one variation of the stimulus. Such a procedure, by its very nature, increases the probability that the subject will begin to guess which aspects of the experiment are being systematically varied by the experimenter. Many studies avoid this problem with what is called a Blind Subject technique. Using this approach, subjects are not told specifically what the hypotheses are. Additionally, subjects are not told what specific experimental conditions they are in. For example, a subject might be told that he/she is supposed to determine which stereo system sounds better, when in fact the experimenter wishes to examine which color or appearance of the same components looks better to subjects. When both a Partial Blind Experimenter technique and a Blind Subject technique are used at the same time, this is called a Double Blind experiment. Double Blind experiments have higher probability of producing statistically valid results than Partial Blind Experimenter alone, Blind Subject alone, or other techniques. Double Blind experiments are highly recommended. 19.3 Where can I get a service manual for brand XXX? The most reliable source of supply is the manufacturer's sales office in your country. 19.4 Where can I get good repairs on brand XXX? 19.5 How can I take 115V gear over to a 230V country or vice versa? Some equipment is available with an international power supply, which can be rewired by any serviceman to either power line voltage. If you expect to be moving abroad, look for this kind of equipment. Often, the same model is available both as US only and as International. Some equipment will be rewirable and won't say it. Adcom amps are known to be rewirable. If you know that your gear is limited to one power line voltage, you can order a new power transformer for that receiver, CD player, amplifier, or tuner which will be wound differently. Contact the manufacturer's local service center. This can be very expensive. A new transformer for a 40 watt receiver would wholesale for under $25 but cost $75 from a service center. Another alternative is to buy a power transformer that will convert 115V to 230V and vice versa. This is only practical for smaller gear. Larger power amps require prohibitively massive and expensive transformers. Also, the addition of a transformer may hurt the sound quality. Here are some common transformer models and 1992 list prices. Power ratings are total line current multiplied by line voltage (2A at 115V is 230 watts). Larger transformers cost more. Some of the costlier transformers are constructed with plugs and jacks for immediate use. Those marked * have wire leads and need safe connections to be used. Before spending money, check into other things about audio in the new country. Broadcast frequencies are slightly different in some countries than in others, so a receiver or tuner bought in one country may not be able to receive some or all of the stations in another country. The US separates the AM broadcast band frequencies by 10kHz while the UK uses 9kHz. Similarly, the US separates FM stations by 200kHz, where the UK has stations on a 50kHz spacing pattern. It MAY be very simple to modify a receiver from US to UK spacings, but may not. Last, but not least, some equipment will NOT work well on 50Hz power. Step Down (230V in, 115V Out) MagneTek/Triad N1X* 50 Watts $11.83 Stancor P-8620* 50 Watts $14.16 MagneTek/Triad N3M 85 Watts $29.95 Stancor P-8630 85 Watts $43.65 MagneTek/Triad N6U* 200 Watts $25.72 Stancor P-8632 200 Watts $51.80 MagneTek/Triad N5M 250 Watts $42.60 Step Up (115V In, 230V Out) Stancor P-8637 85 Watts $43.10 MagneTek/Triad N150MG 150 Watts $49.46 MagneTek/Triad N250MG 250 Watts $54.69 Stancor P-8639 300 Watts $55.51 The Stancor and MagneTek Triad lines are carried by large electronic distributors. 19.6 Are there really good deals in country XXX? 19.7 How do I find out how much an XXX is worth? There is a "Blue Book" for used audio equipment called "Orion Blue Book-Audio". This guide lists both a wholesale and a retail value for most audio gear. Orion Research Corporation 1315 Main Avenue Suite 230 Durango CO 81301 USA 303-247-8855 Last I knew a guide costs $150. Each Nov, a new book is printed. After August, the old book is discounted. If you need a single quote from the Orion Blue Book, send a polite request to: al@qiclab.scn.rain.com and you may get a quote back by e-mail. 19.8 Do people really hear those differences? Who knows? They sure think that they do. 19.9 Why do people disagree on what is the best sound? There are at least three different measures of what is "Perfect Sound". All three have advocates, and all three are right, in their own way. In general, whether they admit it or not, most listeners fit into one of these three preference groups: 1. It must sound like live music. These people know what voices sound like in person, they know what instruments sound like without any amplification, and they have heard orchestras perform unaided by sound systems. They want to accurately reproduce that sound. 2. It must sound like the recording engineer wanted it to sound. The recording engineer listened with extremely good equipment to the sound coming out of the microphones, and mixed them together for what he, at that time, felt was artistically correct. It may not have been the same as live, but it was exactly what he wanted. In the extreme, people like John Fogerty used to audition his final recording mix in his truck to see how it would sound through a common, lousy stereo. 3. It must give me the most pleasure. No matter how good or bad live sounds, no matter what the recording engineer intended, if buy some equipment will give me more listening pleasure then it must be the best. With these three perspectives, it is clear that no one system will satisfy everyone. Add to that confusion the variable that everyone likes a different kind of sound, has heard live music under different conditions, and has a different idea of what the engineer intended. There is an enormous range of possibilities. Another set of reasons is that people look for different things to be right. Some want strong bass; others want male voices to sound like male voices; others want violins to sound like violins. Systems rarely do everything equally well. Speakers (in particular) are compromises. Look for the speaker where the designer had your priority first. You are perfectly right to select speakers based on YOUR personal taste. Confounding the situation further, we all say the greatest things about the stuff we already bought. To do otherwise would be to admit that we are either stupid or deaf. Still another reason is that most people haven't heard enough variations. Until you hear a system that can truly reconstruct the three-dimensional accuracy of a stereo image accurately, you may never realize that it is possible. Some excellent recordings contain enough information that with a good enough system, you can hear up-down, in-out, and left-right distinctions very clearly. However, we will never experience this until we are fortunate enough to hear such a fine recording on a very good system. Finally, some of us really can't hear much difference. We aren't deaf, but we don't have a well trained ear, don't know exactly what to listen for, and may even have slight hearing deficiencies, such as bad sensitivity to high frequencies which comes with older age, or hearing damage from listening to loud sounds (machinery, rock concerts, etc). 19.10 How do I contact the manufacturer of XXXXX? How do I get repair service on XXXXX? How do I get replacement parts? Some magazines publish lists of contact phone numbers for the manufacturers of equipment. In the US, Consumer Reports has a small listing in each issue and a more comprehensive listing in their March issue. Also, Audio Magazine has an exhaustive listing in their October "Equipment Directory". In Europe, look in "What HiFi?". You can find many addresses by reading ads in hifi magazines. You can also find out by asking at your friendly local hifi shop, especially if you've built up a relationship with them. There is a book called the "Electronics Industry Telephone Directory". It comes out yearly and is available in some libraries. Many reps from parts distributors pass them out for free. If you want a copy and are willing to pay for it, call Harris Publishing, 800-888-5900 or 216-425-9000. The directory of the Electronic Industries Association is similarly useful. You can reach the EIA at 202-457-4900. A good source for parts and service is often the manufacturer's repair center. The best way to locate one near you is to look at the literature which came with your equipment when it was new. Failing that, see the ideas mentioned above in 19.10. There is an old list of addresses and phone numbers called "Music Equipment Mail/Phone List". This is posted periodically to news.answers, and contains many addresses of equipment manufacturers. This list is also periodically posted to some music newsgroups. If you don't see it posted at your site, you can get a copy by sending a request to its maintainer, rsk@gynko.circ.upenn.edu (Rich Kulawiec). 20.0 Network Protocol 20.1 What are the other newsgroups on audio and music? rec.audio.pro: This newsgroup is dedicated to professional audio. It includes discussion on record production, studios, studio equipment, DJ equipment, recording concerts, sound reinforcement, mastering, mixing, special effects, and other topics which might apply to audio professionals. If you are a home audio buff but like tape recording, you can find good advice here. rec.audio.high-end: This newsgroup caters to audiophiles and serious music lovers who are interested in discussing the subtle differences between expensive equipment, the nuances of selecting the best cables, the love and lore of LPs, and other details of audio that are inaudible to the untrained ear. rec.audio.car: This newsgroup supports discussion on different brands and models of car stereo, and also is an open forum for talk about car stereo installation, speaker selection, custom crossovers, and the special noise problems which occur in cars. 20.2 What network mailing lists are out there which aren't on usenet? There is an informal group of people interested in using DAT recorders to record "Grateful Dead" concerts. These people call themselves "Dat-Heads" and have a daily E-Mailing List. To subscribe to this list, send a message to: DAT-Heads-Request@fuggles.acc.Virginia.EDU asking to join the mailing list. There is also a general turntable chat mailing list. To subscribe to this list, send a message to: analogue-addicts-request@vortex1.exeter.ac.uk asking to join the mailing list. 20.3 Should I post a question about "XXXXXXX"? If it is related to professional audio, take it to "rec.audio.pro". If it relates to very expensive audio equipment or a request for opinions on subtle sound differences, you might want to take it to the newsgroup "rec.audio.high-end". If it's related to car audio, there's rec.audio.car. Otherwise, if it isn't addressed in the FAQ and it isn't a question for one individual, do it! 20.4 How can I suggest a change to the FAQ? Send an E-Mail message to neidorff@uicc.com and explain your suggestion or correction in detail. 20.5 Where is the FAQ for rec.audio archived? | This FAQ is available by ftp from rtfm.mit.edu in /pub/usenet/news.answers/AudioFAQ To get the entire FAQ from this archive, you need to get all four of the following files: part1 part2 part3 part4 20.6 What does FAQ stand for? FAQ stands for "Frequently Asked Questions". It is assumed that a FAQ also contains FGA or "Frequently Given Answers". The newsgroup rec.audio has very few FGAs due to the personalities involved and the nature of audio. For that reason, this document is called a FAQ. 20.7 Why did I get a bitter reply when I posted a simple opinion? Some feel that rec.audio is populated by people with very strong opinions. The whole audio industry is filled with opinionated people. However, for the most part, these people like voicing their opinions and reading others. What may have sounded like a severe rebuttal may have instead been an outlet for the other person's frustrations or a challenge to you to "play the `rec.audio' game" and back up your words with some spirit. Be sure to stay light when reading rec.audio. Otherwise, you are likely to take yourself and everyone else too seriously. | 20.8 Can I post a "FOR SALE" notice on rec.audio? | In general, yes. Usenet is not for commercial purposes, so if | you are a store or other retail operation, this is the wrong | place for your advertisement. If you have some used gear or | something you bought and don't need, feel free to post it. | | If you see an advertisement for a store that has a great deal, | AND people had been asking about where to buy that item cheap, | you might want to tell the readers on rec.audio about it. | However, try to avoid commercializing. Something like: | | Pete's Audio has JVC PS992 for $435, which is 40% | less than anywhere else; If interested 202-555-1212. | | should be fine. Try to avoid posting their entire price list, | or using too many superlatives. If commercialism leaks into | Usenet, it could materially hurt us all. | | When posting something for sale, have a concise but complete | subject line. Come to think of it, this is good advice for | any post. Here are some good examples: | | Subject: 4Sale Power Amp PS 352 $500 San Francisco area | Subject: 4Sale Carver 100W Receiver nearly new | Subject: 4Sale Stereophile Back Issues 4/88 to 6/92 | | Think about who you are willing to sell to before you post. | If it is fragile or heavy, you may not want to ship it, so you | may restrict to people who are close enough to pick it up. | Use the Distribution: header to restrict your posting area. | If you will only sell to people in Texas, don't distribute it | to Australia. Check with your system administrator if you | aren't familiar with the options you have for Distribution. | Different sites have different restriction codes available. | Distribution headers don't always restrict distribution, so | it is still a good idea to include the target area in the | Subject. | | Anyone buying or selling needs to understand that Usenet | contains no mechanism to protect the buyer's money or the | seller's property. | | There is a frequently posted message "A Guide to Buying and | Selling on Usenet" which talks of other issues on the subject. | This is posted to news.answers as well as other newsgroups. | It is also available by ftp from "rtfm.mit.edu" in | "/pub/usenet/news.answers/radio" as file "swap-guide". -- Leo Breebaart -- Moderator rec.music.info Submissions & other mail to: rec-music-info @ cp.tn.tudelft.nl !!! Requests for information do *not* belong in r.m.info! !!! ******************************************************************************