TAPE GUIDE (Sept. 1985)

Continuous-Loop Cassette, Anyone?

Q. I am interested in locating a continuous-loop cassette at least 30 minutes in length. Is there such an animal? If there is, where can I locate it?

A. What you're looking for is actually called an "endless" cassette. Since this is used in answering machines and automatic display devices, you'd probably have better luck at office products or audio-visual dealers, rather than at audio or other consumer stores. The tapes are usually Type I. They may not last as long as regular cassettes and may not allow rewinding, but they do exist. On the other hand, perhaps your needs could be met by a deck with automatic reverse.

Cold Effects

Q. What are the effects of extreme cold--freezing or below freezing temperature--upon tape? Would this adversely affect fidelity?

A. To my knowledge, cold temperatures within the range ordinarily encountered by humans will have no bad effects. However, tape exposed to extreme cold should be allowed to come up to room temperature before being used. May I suggest an experiment? Take a tape that you don't value, put it in a freezer for one day, bring it out, allow it to come up to room temperature, operate it, and note yourself what adverse effects there are, if any.

Dolby Mistracking

Q. My cassette deck has switches for tape type and for Dolby B and C NR. I have been using Dolby C NR and a well-known brand of normal-bias (Type I) cassette. I recently began using CrO2 tapes, again with Dolby C, and noticed a slight loss of treble. I shut off the Dolby system and tape hiss returned, but so did the high-frequency response. Cymbal crashes, fade-outs, and quiet passages were clearer and steadier, and the music in general was more transparent. Is this to be expected, or is there something I can do about it?

A. I think you have a problem of Dolby mistracking with the particular type and brand of tape that you switched to. Dolby employs variable treble boost in recording, then uses a complementary, variable treble cut in playback to restore flat response while reducing noise. The amount of treble equalization varies with the treble signal level. Accordingly, the record and playback levels going through the Dolby encoding and decoding circuits have to be matched so that the playback treble cut matches ("tracks") the record treble boost.

A qualified technician should be able to check your deck and adjust it, if necessary, for correct Dolby tracking with the particular type and brand of tape you plan to use. If you don't wish to go to this trouble and expense, you might experiment with other tapes. The degree of Dolby mistracking will vary among types and brands of tape because of varying tape sensitivity (amount of tape output for a given amount of signal input to the tape). This is one of the reasons why some deck manufacturers recommend specific tapes for their decks.

Excess Speed

Q. My open-reel deck has performed admirably for over 5 years, but now I have a bit of a problem. The deck is running at about 10 ips regardless of the position of the speed control or the pitch control. I wonder if you have any idea of what could cause this. I usually do my own repair work on all my equipment.

A. If you have been through this kind of repair work before, perhaps an eyeball exam of the transport will reveal the reason for faulty operation, such as a slipping belt, inoperative lever or cam, etc. First, though, purchase a service manual from the manufacturer to serve as a guide in locating and remedying the trouble. Also, you might consult the manufacturer by mail or telephone.

Equating Channel Levels

Q. When recording, should I always strive to set the two recording levels at "equilibrium" even though the level of the original source is significantly higher in one channel than it is in the other channel?

A. If the channel levels of the original source are unequal, and if in your judgment this is undesirable, the record gain controls should be adjusted to achieve the desired balance, rather than turned up equally.

From B to C

Q. I have just purchased a cassette deck with Dolby C NR. I have another deck with Dolby B. Can I dub a cassette with Dolby B noise reduction onto a cassette with Dolby C, and vice versa?

A. Play the Dolby B NR cassette with the old deck in the Dolby B mode.

Feed the signal from this deck into the new deck and record with Dolby C NR on. This will produce a Dolby C cassette. Reverse the procedure to make a Dolby B dub of a Dolby C tape.

Tape Wear

Q. Do metal tapes wear cassette deck heads more than other types of tape? Does rerecording (after erasing) cause the sound quality of cassette tapes to deteriorate?

A. So far as I have been able to ascertain, metal tape causes no more wear of tape heads (and guides, etc.) than do the other tape formulations.

Although tape does not last forever, a tape of good quality can normally undergo hundreds of passes (recordings and playbacks) before noticeable deterioration occurs. To an extent, physical tape wear depends on the deck, that is, on the manner in which the tape is handled with respect to tension, head contact, etc. Magnetic characteristics are essentially unaffected by use unless substantial amounts of oxide have been worn away.

Correction

To convert white noise (equal energy per frequency) to pink noise (equal energy per octave), the white noise should be rolled off by 3.01 dB per octave as frequency rises, not 6.02 dB per octave as stated in the July [1985] "Tape Guide."

(Source: Audio magazine, Sept. 1985, HERMAN BURSTEIN)

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