Tape Guide (Q and A) (Jul. 1972)

Buying in Vietnam

Q. I am in the market for a complete stereo system, including tape components.

I am presently in Vietnam and want to take advantage of the prices here. I'd like some advice from you on what to buy.

-Benjamin Novak, APO San Francisco, Cal.

A. I cannot offer you advice on specific items of audio equipment. The only suggestion I can make is that whatever equipment you decide to buy (based on your own listening, on equipment reviews in audio journals, etc.), make sure that it is widely sold in the United States (if not made here) so that you will have no difficulty in getting this equipment serviced at a future date. I get quite a few letters from persons who have purchased foreign equipment at bargain prices, only to find on their return to the U.S. that their bargain disappears because of the difficulty of finding appropriate service.

S/N = Low Noise?

Q. I am looking for a low-noise tape deck. Just what is "low noise?" Is it right to assume that the higher the S/N ratio, the lower will be the tape hiss and other noise on playback and on record/playback? What is the truth about S/N ratio? One tape machine advertises 55 dB S/N, another advertises 62 dB, and still another advertises 78 dB! Yet all three are in the same price category. It seems to me that the tape head influences the S/N ratio more than anything else.

-Dan Weller, Brewerton, Wash.

A. You are correct in that the higher the S/N ratio the lower is the noise.

In comparing specifications of, say, two tape machines (assuming they both tell the truth), you have to be sure that they both use the same reference level.

For home machines, the common reference level is a 400 Hz signal which results in 3% harmonic distortion on the tape in recording. Some machines, however, use a lower reference level, usually 1% harmonic distortion. Such a machine will claim S/N about 6 to 8 dB lower than a machine which employs the 3% reference. To illustrate, a machine which uses 1% as the reference and claims 50 dB S/N is comparable …which uses 3% as the bout 56 to 58 ….

There are many factors, including the tape heads (particularly the playback head), which enter into the achievement of high S/N. In the case of the playback head, an important factor is the amount of signal it delivers, so that the signal may override noise produced by the tape machine electronics. Noise further depends on the quality of components in the tape electronics (resistors, transistors), on the design of the electronics, on the tape speed, and on the tape used.

15-Min. Dirt Build-Up?

Q. My problem concerns an 8-track stereo cartridge player, the Drexel Model 809. The playback head gets very dirty after a short period of playing, about 15 minutes. A dealer told me it could have been dirty tapes, but the problem happens with brand-new tapes. I have tried cleaning the head with alcohol and have used a tape cleaning cartridge, but nothing helps. If I let the unit play for about two or three tapes without cleaning the head, I can hardly distinguish what is being played This problem has existed from the day I bought the unit. Any help would be greatly appreciated.

- Clyde DePhillips, Jr., New Orleans, La.

A. The problem seems to be a built-in one, resulting from the design of your cartridge player. You may be getting excessive oxide deposits on the head due to too much pressure of the tape against the head, or perhaps as the result of the head not being sufficiently smooth. All heads require cleaning at intervals, but every 15 minutes is far too frequent. It seems you have a perfect right to complain to your audio dealer and to the manufacturer of the machine.

Equalization Change

Q. I have a Sony 355 3-head tape deck. I changed the bias to correspond to Scotch 203 tape. I found that I also had to change my equalization for proper playback. My question is what good is the NAB playback characteristic if the equalization must be changed when bias is changed? Is the recording characteristic supposed to be changed when bias is changed so that I can play back through the NAB characteristic?

-Wayne Chew, Troy, N.Y.

A. You should not change playback equalization when changing from conventional to low-noise tape. Presumably your machine had correct NAB playback equalization before you made changes. This playback equalization implies a corresponding recording characteristic, not in the machine but on the tape. Depending on the kind of tape, bias and record equalization have to be adjusted. The test of the correct recording characteristic is whether you get flat response in playback. I suggest that you restore your machine's playback equalization to NAB response; this can be done by playing a test tape and adjusting playback equalization for flattest response.

Then, using low-noise tape, adjust bias and record equalization (and audio drive current) in accordance with instructions provided by the manufacturer of the tape or of your machine; adjust record equalization for flattest record playback response.

Miking A Meeting

Q. Can you advise me about a microphone for use in recording business meetings with a battery operated cassette recorder? Generally these meetings will involve only two or three people, but there could be as many as six or eight.

-David R. McClurg, Mountain View, Calif.

A. I suggest that you buy one of the better ceramic microphones or one of the cheaper dynamic microphones. Something in the class of roughly $10 should serve your purpose nicely. The microphone should be of the omnidirectional type, as most inexpensive ones are, for your application.

Low-Noise Tape

Q. What tape companies put out low noise tape so that you can record at lower speeds?

-J. David Newman, Berrien Sprints, Mich.

A. Low-noise tape has nothing to do with recording at lower tape speeds.

It is simply tape that, to the human ear, apparently produces less tape hiss and other tape noise than do conventional tapes.

(Audio magazine, Jul. 1972; Herman Burstein)

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