TAPE GUIDE (Aug. 1990)

Setting Record Level

Q. What is the proper way to set record level? Should I set it once and use the same setting throughout the tape, or should I reset it for each cut? I usually set the level at the beginning of recording, but on playback my deck's meters go up to maximum on some cuts and down to -5 or -7 dB on others.

-John DeRosa; Mattapan, Mass.

A. I am not sure what you mean by "cuts." Do you mean sections of a phono record or CD? If these sections are related, such as movements of a symphony or parts of a song cycle, then it is best to set record level at the beginning and leave it alone throughout taping. However, if the cuts are unrelated, such as a collection of popular songs originally recorded at various times and places by one person, it would be appropriate to set the record level individually for each selection, if you wish.

Still, this isn't really necessary, because tape decks today provide such a high S/N ratio that it isn't important to get the last iota of recording level on the tape in order to maximize S/N. Wasting a few dB of S/N isn't likely to interfere with listening pleasure.

Back in the days before noise reduction, when the best S/N ratios you could get from tape decks were relatively low--around 50 dB and sometimes even lower--recordists would sometimes "ride gain" when taping.

That is, they would keep the record level quite high to maximize S/N, and they would temporarily reduce gain during crescendos (assuming they knew loud passages were coming) to avoid tape saturation, with consequent distortion and treble loss. This resulted in a loss of dynamic range, but such a loss was often considered preferable to the insistent hiss and hum of tape recording when the state of the art was less developed. Today, though, S/N is generally high enough that one can afford to under-record.

Transplanting Heads

Q. I am considering transplanting the heads from one cassette deck to another. The donor is a deceased three-head deck, and the recipient is a two-head model. A four-pole double throw switch would be added to alternate the head between record and playback. Aside from mounting and alignment problems, might this work? Should I expect irregularities in frequency response?

-Mark Slagell, Madison, Wisc.

A. Assuming that you can satisfactorily mount and align the replacement heads-not an easy task-I think they have a good chance of working adequately, provided that you use the former playback head as the new record/playback head. The playback head has a much narrower gap than the record head--roughly one-fifth as wide--and this is essential to preserve high-frequency response in playback.

On the other hand, the playback head may have too narrow a gap for good recording, which would increase distortion and reduce response in the lower audio range. The narrow gap tends to act as a short-circuit, preventing the magnetic field from penetrating the tape as deeply as it should. For this reason, heads designed for combination record/playback use have somewhat wider gaps than those intended solely for playback. (To illustrate, a record/playback head might have a gap 1.2 microns wide, whereas a playback only head might have a gap of 1 micron or less. The narrower the gap, the better the high-frequency response in playback. The difference between gaps of 1.2 microns and of 1 micron or less is of consequence.) Bias employed in recording will probably have to be changed to obtain suitably low distortion along with suitable high-frequency performance. It may be more difficult to drive the required amount of bias current through the new (formerly playback-only) head than through the old record/playback head, requiring an increase in current supplied by the oscillator-or it may be the other way around. Also, it may be necessary to adjust calibration of the record level indicators so that they will adequately indicate maximum permissible recording level. This is because the strength of the magnetic field applied by the head to the tape will vary with the head that is used.

(Source: Audio magazine, Aug. 1990, HERMAN BURSTEIN)

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