Tape Guide (Jun. 1981)

Quality Control Patrol

Q. I have been having a problem with two well-known brands of cassette tape which have been jamming in my deck, yet two other well-known brands have given me no such problem. Is there such a thing as quality control any more?

-Albert Brown; Brooklyn, N.Y.

A. Over a long period of years I have been hearing from time to time about combinations of components that are highly regarded individually yet don't work well together. For example, one may hear about a certain top-flight power amplifier that just doesn't work well with a certain much-acclaimed speaker (oscillation, blown fuses, etc.). Or one may hear about a tape that squeals with a certain tape deck, although it is very quiet with other decks. Perhaps you have one of these luckless combinations.

But there are other possibilities. Perhaps your cassette deck is at fault. You can check by playing the offending cassettes on other decks; hopefully your audio dealer will be cooperative in this respect. If the same cassettes still jam on other decks of your model, but don't jam on other brands and models, it would appear that it is your model line which is at fault. If they jam in all cases, it is clearly the cassettes that are at fault. If the cassettes jam only on your deck, then this is where the faultlies. And the deck should be brought in for repair or exchange--preferably exchange.

Another possibility is that you were unlucky enough to get several cassettes out of a bad batch, owing to a lapse in quality control. But since this happened with two different brands of tape, the possibility, although it still exists, be comes quite remote.

Trade-Offs

Q. I am in the market for a cassette deck. What should I take into consideration pertaining to bias and distortion?

-Amos Perrine; Huntington, W. Va.

A. Of course, you want a deck with as low distortion as possible in recording and playback. In recording, distortion ties in with bias, Sometimes, in order to get extended treble response, a manufacturer may underbias excessively, re suiting in too much distortion. A good deck seeks an optimum combination of low distortion and extended treble through careful choice of bias, treble boost in recording, and recording level.

Signal-to-noise ratio is also involved; thus a reduction in recording level in order to reduce distortion will also de crease signal-to-noise ratio. In view of the variety of cassette tape coating formulations, it is desirable to have considerable flexibility in choice of bias as well as record and playback equalization.

Playback equalization should offer a choice between 120-µs equalization for ferric tapes and 70-uS equalization for chrome, ferrichrome, cobalt-modified, and metal tapes.

Alignment Line-Up

Q. Where are alignment tapes available?

- Jerry Pulice; Staten Island, N.Y.

A. Test tapes of various kinds and at various prices are available from:

Ampex, 401 Broadway, Redwood City, Cal. 94063; Taber Manufacturing and Engineering, 2081 Edison Ave., San Leandro, Cal. 94577; Magnetic Reference Laboratory, 999 Commercial St., Palo Alto, Cal. 94303; Nortronics, 8101 10th Avenue North, Minneapolis, Minn. 55427; Audiotex, 400 South Wyman St., Rockford, Ill. 61101; TDK Electronics Corp., 755 Eastgate Blvd., Garden City, N.Y. 11530, and Magnetic Information Systems, 415 Howe Ave., Shelton, Conn. 06484. This is not necessarily a complete list.

Un-Dolbyized

Q. If I make a cassette recording with Dolby NR on, is it harmful to play the tape back with Dolby NR off? Conversely, if I record with Dolby NR off, is it harmful to play the tape with Dolby NR on?

-Richard Paul; Philadelphia, Pa.

A. I am not sure what you mean by harmful. If you refer to physical or electronic damage to your equipment, there is absolutely no harm in playing without Dolby NR a Dolby-encoded tape, or in playing with Dolby NR a tape that has not been Dolby encoded.

If you refer to frequency response, yes there is often harm. If a tape has been Dolby encoded and is played with out Dolby encoding, the result is an in crease in brightness, in treble response.

Alternatively, if a tape has not been Dolby encoded but is played with Dolby decoding, the sound is dulled, a decrease in treble. On the other hand, your ear might find one effect or the other to be pleasing. For example, if your speakers are overly bright, you might find a slightly dulled sound beneficial when playing tapes that are not Dolby encoded.

Real Old Reels

Q. I have several tapes made with an old open-reel deck. Will these play back properly on a new deck?

-John Etnier, South Harpswell, Maine

A. Any tape that has been properly recorded, that is with the NAB recorded induction characteristic, will play back flat on a deck that supplies the NAB playback characteristic for the speed in question.

Print-Through and Through

Q. Many of my cassette recordings have a delayed echo on side 1--that is, a repeat of what is said, several words behind, at a very low volume but audible and annoying. When I flip to side 2, rather than an echo I hear an anticipation of what will be said--starting several words ahead. I use good tape. The problem seems worse on older tapes but is discernible on new ones as well. Can you advise what the problem may be and how to solve it?

-Wendy Rickert; Boulder Creek, Cal.

A. Your problem is called print-through, wherein the signal on one layer of tape is magnetically transferred to adjacent layers. Whether you get pre-echo or post-echo depends on whether the tape is rewound before storage or left in the played condition.

Print-through tends to increase with time, approaching a limit. Print-through tends also to increase with magnitude of the signal level recorded on the tape and with decreasing thickness of the tape.

Therefore, measures to minimize print-through are to avoid high recording levels and to avoid the very thin tapes, such as C-120. (There are additional reasons for avoiding the ultra-thin tapes, involving distortion, squeal, etc.) For a given type of tape and for a given recording level, some brands of tape may be less susceptible to print-through than others.

Trial and error are necessary to find out which tapes are best. To some extent, existing print-through can be reduced by shuttling the tape back and forth prior to playing. A slow shuttling at operating speed is recommended.

Because of print-through, accumulating physical stress and other reasons, it is a good idea to play a tape periodically, say every few months, rather than let it stay in storage indefinitely.

(Adapted from: Audio magazine, Jun. 1981; Herman Burstein )

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