TAPE GUIDE (Aug. 1988)

Azimuth Alignment by Ear

Q. I have an azimuth alignment problem in my car deck. Is there any way I can correct the problem myself? The deck has an azimuth alignment screw.

-Dominic Ruffolo; Somerdale, N.J.

A. You can probably do a pretty satisfactory job of adjusting azimuth by ear. Play a commercially recorded tape with abundant highs, and gradually adjust azimuth in one direction or the other until you obtain maximum treble response. (You will have to determine which is the correct direction experimentally.) If the majority of tapes you intend to play in your car are those recorded on a home deck, however, use one of your own tapes, instead, for azimuth alignment of the car deck.

In adjusting azimuth, watch out for what is called a "false peak." As you adjust in the correct direction, you may obtain a peak in response followed by a decline. However, if you were to adjust further in the correct direction, you might come to a greater peak, i.e., the true peak in treble response which corresponds to correct alignment.

The best procedure is to adjust azimuth on the basis of a test tape with a high-frequency tone such as 12 or 15 kHz. But such tapes are quite expensive and, further, you'll need an audio voltmeter to measure playback response--unless the deck incorporates a meter that indicates this level. However, as I mentioned, you can usually do a pretty good job by ear. And if you are off just a little from perfect alignment, it probably won't matter in a car.

Longevity

Q. Does the sound of audio cassettes degrade with time? If the tapes are stored properly, will the passage of five or 10 years have any effect on the treble, bass, or overall volume of sound? Do I stand a better chance of escaping such effects by using Type II or Type IV tapes rather than Type I tapes?

-Anthony Hudaverdi; Santa Monica, Cal.

A. My understanding is that present-day high-quality tapes are almost impervious to frequency change with time and use. There may be a very slight loss in the extreme high frequencies, but it's usually too slight to be noticeable. The stability of a tape over time depends primarily upon its coercivity, i.e., its resistance to magnetization and to demagnetization. Accordingly, Type II and, especially, Type IV tapes would be more stable than Type I. Another factor is the binder that holds the magnetic coating to the polyester base. Advances in binder chemistry have enabled the magnetic coating to achieve high stability over a substantial range of temperatures and humidity levels.

In the past, with repeated playings, there were reported problems of high-frequency losses due to magnetostriction (changes in the tape's magnetic properties with stress and strain). I understand that such losses have been minimized.

VCR Taping

Q. I use my hi-fi VCR as a second audio tape deck, with excellent results.

Its specs rival or exceed those of the majority of open-reel decks. Does performance change significantly from one tape speed to another? Also, what are the actual tape speeds for the SP, LP, and EP [standard play, long play, and extended play] modes?

-Mark H. Johnson, Cape Cod, Mass.

A. Whether the quality of audio recordings made on a VCR changes audibly with tape speed depends on the particular VCR and videotape you are using. In general, there will be little significant change, often too little to detect by ear. Tape dropouts are apt to be more discernible at the slower speeds, but even so, when using good tape, these tend to be very infrequent.

The thing to do, really, is to experiment with your VCR and chosen tape to find out whether you experience a noticeable reduction in audio quality as you go from SP to LP to EP. In the VHS format, the tape speeds for SP, LP, and EP are, respectively, 1.32, 0.66, and 0.45 ips. In the Beta format, they are 1.54, 0.79, and 0.53 ips. However, the heads rotate several hundred times per minute, so the tape speed relative to the heads is much faster than these figures.

(Source: Audio magazine, Aug. 1988, HERMAN BURSTEIN)

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