By Larry Klein
Altec Lansing's speaker evaluation racks in one of their test/listening rooms.
Inaudible Noise
Q. Considering the effect synthesizers have had on popular music as well as progressive jazz, I was curious about your opinion on a subject I have been working on. It has to do with the possibility of using "inaudible noise," refined in such a way that it would, fall into the frequency range of human hearing, with conventional contemporary music. Your comments, personally or in your column, would be greatly appreciated.
MICHAEL S. EITLAND; Loring AFB, Me.
A. Maybe I've missed your point, but do you really mean that there isn't enough audible noise out there for you to play with? Really? Hard-rock Tracking Force r'' A recent "Audio Basics" column dealing with tracking force raised a question that I'd like an answer to. I'm a hard-rock fan, and I was wondering if there should be a different tracking force for the "bumpy" rock discs than for "normal" or easy-listening discs.
This may seem a silly question, but I've noticed a bit of distortion in the louder parts of hard rock, and slower music seems to come through distortion-free.
RAY AKERS; Elliston, Va.
A. tracking force required in a given record-player is simply that which is necessary for the stylus to track the record groove accurately. This in turn is determined by other forces in the playing process that tend to drive the stylus out of the groove. To put it another way, the applied vertical tracking force must at all times be greater than the various forces that cause the stylus to lose contact with (mistrack) the groove. It's the mistracking that produces the distortion you hear. The forces contributing to mistracking can be divided into those that affect tracking at low frequencies and those that affect it at high frequencies. The low-frequency problems are usually the unsubtle ones; the stylus "sticks" or jumps grooves, or it reproduces a variety of low-frequency thumps, bobbles, and wavers that aren't, as you'll find, really on the record. These problems are almost al ways caused by record warps, too low a tracking force, improperly set antiskating force, a bad mismatch between the tone arm and phono cartridge, or a combination of these factors.
The high-frequency tracking problems result in very sibilant "sss" sounds and a sort of break-up quality on some loud, high-frequency passages. Loud high frequencies are em bodied on a disc in the form of very rapid undulations in the record-groove walls. If the moving part of the phono stylus has too much mass-and hence too much inertia-to follow the rapid twists and turns of the groove, it will momentarily loose contact or bounce from peak to peak when things get rough-which is at the loudest and highest frequencies. Applying more vertical tracking force will push the stylus into the groove and may produce more reliable contact during hard-rock stress conditions. But keep in mind that any vertical-force increase must be kept within the range of the cartridge's rated tracking force. If the manufacturer rates the cartridge for 1 to 2 grams tracking force and the distortion is still heard at two grams, it may mean that your ear is better than your cartridge (and one or the other should be replaced), your tone arm needs help, or the record has been so overcut that no cartridge will play it cleanly. In any case, may the tracking force be with you.
Planned Obsolescence?
Q. I own an integrated amplifier that shortly will be ten years old, and I use my equipment at least five hours a day and more on weekends. How does age affect the performance of solid-state equipment, and how long well it be before "planned obsolescence" sets in? And which equipment is likely to become obsolete first?
GAYLE W. RARESHEID; Sheffield Lake, Ohio
A Judging from my more than twenty years experience with and within the audio industry, I would say that any equipment obsolescence you encounter will be totally un planned. What you are really asking about is deterioration from wear and aging. Unlike the mechanical parts of an audio system, the electrical parts do not suffer from a wear process.
True, semiconductors and capacitors may develop leakage in time, electrolytic capacitors can dry out, resistors have been known to change value, and controls get noisy. How ever, these problems are seldom aggravated by severe use, but rather result from the nor mal aging process. When something does go wrong, the problem will be heard as noise, intermittent loss of signal, distortion, or simply silence.
It is true that for marketing reasons many manufacturers feel obliged to bring out a completely new line (or replace large parts of their existing line) every year or so. But I've ob served that in addition to the styling changes, the manufacturers almost always provide at least some improvement or price reduction with each new model.
As far as "planned obsolescence" is concerned, I have never seen any radical changes in sound reproduction-for example, the shift from 78-rpm to 33.33-rpm discs or from mono to stereo-that weren't fully validated by the improvements in reproduction brought about by new technology. And even such radical changes almost always allowed the consumer to use much of the equipment from the previous "obsolete" technology.
One other aspect of the question should be mentioned. Not only has the equipment evolved over the years, but, despite inflation, today's hi-fi equipment provides far better audible performance dollar-for-dollar than it did twenty years ago. Phono cartridges and tape machines have improved sonically most of all, followed by speakers, tuners, turntables, and amplifiers. I would say that "state-of-the art" equipment of ten years ago (except for phono cartridges and tape machines) should not be much inferior to today's best equipment. However, low- to middle-price components or heavily used mechanical equipment could probably be replaced with clearly audible benefits after ten years or so.
Stacking Separates
Q. I see that among top-quality stereo components on the market today are separate but matching components normally shown stacked on top of one another. I'm curious as to how they solved the problem of induced hum. I've tried to stack my stereo separates, but the hum proved to be too much.
HOWARD LOO; San Francisco, Calif.
A. Hum will usually be induced when a power transformer or motor radiating an electromagnetic-hum field is placed in close proximity to a very high-gain amplifying stage early in the audio chain. Such a stage might be a phono or tape-head preamplifier section (magnetic phono cartridges and tape heads themselves are also very sensitive to hum fields). As far as radiated-hum prevention is concerned, some types of transformers are specially wound or shielded to minimize their potential as hum sources. And it is of course possible to minimize hum problems by careful physical engineering of the units to be stacked so that one component's transformer is not too close to another's high-gain stage.
As for your particular stacking problem, first make sure that the hum really is caused by transformer radiation. You can determine this by temporarily stacking your units with a piece of insulating cardboard between them.
It could be that the first time you tried stacking them the two components were in electrical contact, which caused a hum-producing ground loop. If hum persists even though the two components are insulated, then you probably do have an electromagnetic-hum problem. If feasible, try reversing the order of the stack. If that doesn't work, you could try constructing a simple hum shield. You'll need a small, flat sheet of thin-gauge iron or steel such as would be provided by a cut-apart and flattened coffee can. (If you can't afford coffee, any non-aluminum can of the same size will serve. Any material that a magnet will stick to is fine.) Simply move the shield around between the components while listening for the hum. Make sure that you don't establish a new ground loop by causing the shield to touch both chassis. You can insulate the shield, if need be, with the cardboard sheet mentioned earlier. If you are lucky you'll find a spot for the shield that interferes with the radiated hum path between the components. But in any case, do be careful not to block off the air flow to and from the power amplifier's heat sinks.
Hi-fi Counterfeits
Q. I recently was told that there are some counterfeit hi-fi products on the market. Exactly what does that mean and how can I avoid them?
TERRI SCHULTZ; Chicago, Ill.
A. Only three examples of bogus brand-name audio items have been brought to my attention, but I'm sure there are more out there. counterfeits were cassette tapes that were packaged to look like high-quality name brands. The same general art work, color, and type faces were used on the cassette boxes as on the brands they were imitating. A KDK brand cassette, if not examined closely, could be mistaken for a quality TDK, a "Maxelite" C 90 was deliberately made to look like the Maxell product, and there are a number of unbranded or "Shure" replacement styli out there available for purchase by unwary Shure cartridge owners. In each instance, the resemblance is only skin deep: a shoddy, cheaply made product is masquerading-and is usually being sold for the same price-as a legitimately expensive, high-quality, precision-made product. The imitation not only does not work as well, but in addition could damage your tape player or, in the case of the counterfeit stylus, your discs.
-------------- A bogus "Maxelite" (top) and the genuine
Maxell cassette. Note the copy-cat packaging.
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Also see: Pioneer SX1250 receiver
AUDIO BASICS: Getting the Room Right--II