Audioclinic (Apr. 1982)

Also Sprach Giovanelli

Each and every letter sent to "Audio clinic" is answered individually. The fact that both Herman Burstein ("Tape Guide") and I are willing (or crazy) enough to take on such a task is part of what makes Audio unique.

Even though each letter is answered personally, space and other considerations limit the number of letters which appear in print each month. Therefore, some of you who write in may be disappointed if your letters are not published or if they appear after a considerable amount of time. Although it may be expedient in some instances to rush a reply, it is only fair that I answer all letters in the order in which they are received.

It may be helpful for you to know that when I do plan to use a given question for this column, I state this in my answer. I also ask the reader if he wants his name published; if he does not, I request that he write me back immediately, and the name will be withheld.

While this imposes a somewhat greater amount of correspondence, I think it makes it less confusing for everyone.

When writing, please note that I cannot become involved with questions related to the merits of specific products. Because this type of judgment is subjective, I prefer more general, objective questions. A lot of basic product information is contained in our Annual Equipment Directory issue in October; many comparisons can be made from an examination of the individual product specifications submitted by the manufacturers. You will also gain added information about a number of products from Audio's Equipment Profiles.

Every once in a while I receive a letter telling me that I did hit the nail on the head in diagnosing a piece of equipment I have never seen. As you can imagine, such diagnosis by long distance has to be based somewhat on guesswork (scientific, but still a guess), and I always wonder how well things have worked out. It's nice, too, to hear from someone who finds that an item published here could have had an added touch to make it a better answer. I appreciate these letters, and from time to time, I incorporate them in "Audioclinic." We can all learn something that way.

-J.G

War on Warp

Q. What is the best way to store phonograph records? I have found that some of the albums I have not played for awhile are warped.

-Joseph Topp; Shorewood, Wisc.

A. The best way to store records is to keep them in an upright position without allowing them to lean over at an angle. The shrink-wrap should be removed from the jackets as soon as you buy the discs. Sometimes this plastic material can be so tight that the jackets and discs warp. But, most particularly, discs should never be stored near sources of heat, such as radiators, because heat can also cause discs to warp.

The Facts of (Recording) Life

Q. I have purchased a number of highly touted digital recordings from different manufacturers. Although each of these is impressive in many respects, I have yet to find even one with totally silent surfaces, as well as the 90-dB dynamic range claimed by manufacturers of these recordings. Silence is total absence of any sound or noise according to my dictionary, but these recordings have background noise and even print-through. Why?

-Brian E. Newman; Burgettstown, Pa.

A. Digital tape recordings can have signal-to-noise ratios of 90 dB. Such recordings, however, are ultimately made with conventional disc mastering and mass production techniques.

Therefore, the dynamic range and certainly the signal-to-noise ratio is limited by the discs themselves and the care taken in producing them. The maximum S/N of a disc is 65 dB, but only if everything is done correctly.

Recordings for the mass market often are produced with mediocre playback equipment in mind. This will often result in other problems in addition to the noise about which you have written. Equalization may be employed which will make the music sound strident when heard on many of our better systems. Unfortunately, there are just too few really good systems around even now to justify the routine production of the highest possible quality disc. While the quality of pressings can be improved in many instances, this would ultimately result in a much higher price per disc, very likely lowering sales at a time when the industry is already suffering from declining sales.

Stacked Speakers and Volume Loss -- II

In response to Mr. Ervin's question, printed in "Audioclinic," March, 1981: One possible reason for the volume loss when both speakers are connected "A plus B" is caused, at least in some cases, by the speakers' being connected in series instead of in parallel. Thus, the amplifier is delivering half the power to two speakers than it delivers to just one speaker. When the equipment is connected in the "A plus B" mode, each speaker receives one quarter the power it would receive in the "A" or "B" mode. This accounts for the loss in volume that you hear.

The parallel connection would correct this volume loss. The series connection, however, affords the amplifier the protection from overheating which could arise because of high power operation into very low impedances.

-Kevin A. Barrett, Plainfield, N.J.

Buzz Words

Q. If I try to use the AM section of my tuner with my external power amplifier turned on, a buzzing noise occurs which disappears when the amplifier is turned off. Could this problem be connected with patch cords, or is the power supply from the external amplifier causing it? The second, or external, amplifier sits on top of the receiver, and both the power transformer and interconnecting patch cords are close to the AM antenna.

Would moving the amplifier help or would an external AM antenna be more beneficial?

-Gerald A. Larson; Bozeman, Mont.

A. The buzzing produced in your AM tuner is probably not created by patch cords; I believe it is related to diode switching in the power supply of your external amplifier. This sound will likely disappear if the two units are separated from one another a bit further than they are now.

You may need to bypass each diode with 0.01-uF capacitors. The capacitor should be connected right across the diode and not from either side of the diode to chassis ground. The voltage rating of the capacitor should be three times the power-supply voltage.

If you are getting satisfactory AM reception using the receiver's internal antenna, I do not suggest that you connect an external antenna to the receiver. The use of such an antenna could result in overloads and spurious responses which would degrade the AM reception.

Oldies Still Goodies

Q. Is it safe to play my 30-year-old mono record collection (which is in very good condition) on my new stereo system?

-Helen Stambor; Lima, Ohio

A. You will be happy to learn that you can play your old mono records on your stereo system; your cartridge will not know or care. The only thing that is likely to happen is that you will hear better sound from those old discs than you heard when you first bought them, assuming that they are indeed in good condition.

While there may be a tendency for the stylus to ride closer to the bottoms of the grooves than was true in the days of the 1-mil stylus tip, this will not cause problems. In fact, it will actually be an advantage because this portion of the groove wall will probably not have been abused by the high tracking forces so common to old monophonic cartridges.

Keep It Simple

Q. I recently added a second power amplifier to my system. My present receiver has provisions for separating the preamplifier section from its power amplifier section. I'm using the power amplifier section of the receiver to drive one pair of speakers and the new amplifier to drive another pair of speakers. Sometimes, the right speaker driven from one of the power amplifiers fails to operate after turn-on. If I wiggle the patch cords, it will finally work. Have I isolated the problem or do I need to look further?

-Gerald A. Larson, Bozeman, Mont.

A. It would appear that you have isolated the problem of your intermittent right channel to either the patch cords themselves or to the connectors associated with them. A defective, molded plug could cause the problem.

The same problem could also be the result of oxidation in the female connector on your patch board or a poorly soldered connection. It is always possible that the jiggling of the patch-cord shock excites some other component into operation. Try the cords first, however, because they are the most likely source of this problem and also the simplest items to repair or change. I always recommend that, in any troubleshooting situation, you try the simplest remedies first.

(Audio magazine, Apr. 1982; Joseph Giovanelli )

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