Shrink Wrap, Companders vs. Dolby, Questions Question
by LARRY KLEIN
Shrink Wrap
Q. I have been warned of the dire consequences of leaving the cellophane wrapper on my albums after I buy them.
However, I have been taping the wrappers onto my precious album covers for nearly a decade now, and I have noticed no adverse effect on my records, which I store vertically, pressed tightly together. Is this cellophane -warping -the -record story just a lot of bunk?
ESTELLA WYATT-WALLACE Dunkirk, Md.
A. The question is simply whether the cellophane "shrink wrap" applied at the time of packaging continues to shrink after the wrapping has taken place. It seems that in some cases it does and in other cases it doesn't, probably depending on local temperature and humidity conditions as well as the type of plastic used. In any case, if you find the shrink wrap stretched tautly around the album cover, you can assume that it is putting undue stress on the record inside. If it is somewhat less than skin tight, there's no problem-though one might develop later. It is possible that your storage method may have something to do with preserving records whose shrink wrap is too tight from the peril of warping.
Questions Question
Q. Sometimes there is a little notice at the end of your column stating that only questions selected for use will be answered. How do you select questions for use, and why not answer the others?
NEIL LARSON Poughkeepsie, N.Y.
A. I'm glad you ask the question(s). The Qs that may or may not produce an A in this column fall into several different categories.
There is a certain number of perennial questions that require at least an annual answer for new readers or those who were not paying attention the last time. Questions about, for example, power requirements, Dolby adjustments, and acoustic feedback fall into this category.
Another type of question regularly finding its way to our in -box (if not this column) asks about some new hi-fi technology featured in a product advertisement. I usually have no ready answer, because in many cases only time will reveal whether the new device or approach is a breakthrough, merely an alternate way of doing something, or a sophisticated solution to a nonexistent problem. (If readers sometimes have difficulty determining whether a given product represents the bluebird of hi-fi happiness or merely some manufacturer's technical wild goose chase, so do we.) Questions of the "which is best" variety do not get column space at all. In general, we confine our remarks on product quality to the test -report section of the magazine. It would be manifestly unfair, given the market clout of STEREO REVIEW, to express opinions based on hearsay, manufacturers' literature, personal prejudice, or anything other than laboratory tests and/or a con trolled listening session. Any reader who wants to know how we feel about a piece of equipment will have to get that information from a test report. If there wasn't any report, it is likely that we know little or nothing more about the product than any one can discover from the manufacturer's literature. (A complete index to all the products we have tested since 1965 is avail able for 35ยข in coins or stamps plus a stamped, self-addressed long envelope sent to STEREO REVIEW, Dept. TRI, I Park Ave., New York, N.Y. 10016.) Another category of question can be distilled down to "I have a hi-fi something that doesn't work right. What's wrong and how do I fix it? . . . or modify it? . . . or match it properly to some other hi-fi some thing?" All these questions get a form reply that says, in part: "Unfortunately, the best we can do is suggest that you write directly to the manufacturer of your unit. Because of his familiarity with his own products, he is in a far better position to advise you on the specifics of your particular question or problem than we could possibly be." It's a mystery to me why so many component owners write to us first when they have troubles. Anyone having any familiarity with electronics knows that most products are likely to have some characteristic "failure modes," and the factory repair people are the first to know what those are and what to do about them.
Then there are those optimistic souls whose five -page, single-spaced, typewritten letters detail their personal hi-fi histories (apparently from the moment they learned to hear) as a preface to their asking me to choose several optimum setups from an included list of thirty or so models. Some readers hasten to add that they will be glad to pay any charges incurred, but others seem to think-or at least hope-that such a service ought to come free with their purchase of a copy of the magazine or a subscription. I guess I could go into detail here as to why we can't oblige our more than a million readers in this regard and still put out a monthly magazine-but is that really necessary? In any case, all mail is at least read, and some of it is answered directly with a form reply or a marginal note. Obviously, those readers who enclose a stamped, self-ad dressed return envelope stand a far better chance of getting a response than those who don't. It seems appropriate to end with another quote from one of our forms:
"We appreciate the confidence you have expressed by writing to us and regret that we cannot be of more specific help." And we really do! Companders vs. Dolby What is the difference between the Q Dolby -B system and the component companders that are produced by several other companies?
ROBERT WARD Laurelton, N.Y.
A. Dolby-B system actually is a type of compander, a compander being a device that compresses a signal's dynamic range when it is recorded (or transmitted) and expands it back to its original form on playback. The Dolby system, unlike most of the other systems, compresses and expands only the low-level, high -frequency part of the signal. In effect, it operates only on that part of the signal where hiss is a problem.
The usual compander operates on all levels of the signal and over the entire frequency range all at once.
Dolby's view is that by ignoring the loud signals, which tend to mask noise anyway, the risk of audible encode/decode errors is greatly reduced. And by operating only on a part of the frequency range, noise -modulation effects are greatly reduced. ("Noise modulation" describes a situation in which the audible noise in one part of the frequency range goes up and down with the signal level of the music in another part.) On the other hand, the amount of noise reduction the Dolby system provides (about 10 dB in the hiss region) is less than most companders provide under low-signal conditions.
Basically, then, both types of compander incorporate trade-offs. The Dolby system is generally considered to be error free, and it is less likely to misbehave. A wide -band compander can provide more noise reduction but may be less tolerant of recorder deficiencies or may need careful adjustment to avoid audible side effects.
Also see: TAPE TALK: Dropouts, Wearing Away the Highs, Output, Tapesponding CRAIG STARK
Source: Stereo Review (USA magazine)