TAPE GUIDE (Feb. 1984)

Squeak

Q. My open-reel deck has worked satisfactorily for seven years, but lately it sometimes makes a squeaking noise which comes from the area of the left reel. This occurs only during normal operation, and not in fast forward or rewind mode. If the squeak occurs when recording, the sound is extremely distorted at this point in playback. What's wrong? I tried spraying the belts with a silicone spray, but this had no effect.

-Phil Mougis, Middle Village, N.Y.

A. While a belt may be slipping, I doubt that silicone spray is the proper substance to apply. Special liquids are sold to remove glaze from rubber materials and enable them to grab more solidly. You might try one of these. However, the belt (if this indeed is where the problem lies) could be beyond salvation and need replacement.

Check whether the tape is rubbing against the flanges of the supply (left) reel, whether the left reel hub is making contact with the chassis, and whether the reel is doing so.

If your problem still persists, you will have to rely on a competent service technician, preferably one authorized by the deck manufacturer to service its product.

Multiplex Filter Use

Q. I use my tape deck for recording from discs and FM. The problem I have is understanding the use of the multiplex filter in my deck. The deck manufacturer recommends using the filter only for FM. Should it also be used for discs, as some articles have recommended?

-Herbert A. Poison; Montreal, Oue., Canada

A. The purpose of the multiplex filter is to eliminate the 19-kHz pilot tone which appears in an FM broadcast. This tone may interact with the Dolby circuitry, producing mistracking, or its harmonics may interact with the oscillator frequency, causing beat frequencies to appear. Some tuners have effective multiplex filters, while others do not. Therefore, cassette decks often include a multiplex filter. This filter will sharply reduce frequencies in the region of 19 kHz and above, usually with negligible effect on frequencies within the hearing range of most of us--say, below 17 kHz or so.

Ordinarily the filter should be engaged only when recording from FM. However, it is possible that use of the filter might add to one's listening pleasure when recording from phono by removing more noise than desired audio signal. Why not try recording both ways and decide for yourself?

Head Cleaners

Q. What is the best solvent for cleaning cassette tape heads, capstans, etc.?

-Glen R. Carnrick, Sandy Hook, Conn.

A. The two items most frequently recommended for cleaning are isopropyl alcohol (91%) and fluorocarbons, in particular trichlorotrifluoroethane.

Probably the best course is to follow the recommendations of your deck manufacturer. Whatever the solvent, it should be one that is safe to use on tape heads, capstans, pressure rollers, and, quoting from one maker of a solvent, "plastics, rubber, metals, painted surfaces, and elastomer parts." (Editor's Note: For a more detailed discussion of this subject, refer to Howard A. Roberson's article, "Tape Recorder Maintenance," which appeared in our April 1982 issue.)

Playback Level Indications

Q. Why do the LED level indicators on my cassette deck always show a lower level (about 2 to 3 dB) during playback than the level at which I recorded? Also, why would the right channel level be consistently higher than the left during playback, even though both were equal when recording?

-Jeff Pagels, Largo, Fla.

A. The level indication in playback will depend on the sensitivity of the tape you are using. Some tapes, for a given signal input, deliver more signal than do other tapes. It may be that the deck manufacturer calibrated the playback indication for a more sensitive tape than the one you are using.

Higher level of the right channel relative to the left channel may be due to mis-calibration in either recording or playback. In playback, the right indicator may read higher for equal signals in the left and right channels. Or, in recording, the right indicator may read lower for equal signals so that more signal has to be fed to the right channel for equal readings when recording.

VU or Not VU

Q. My four-year-old cassette deck has very clear and well-lit VU meters plus a light that turns red when maximum permissible record level (MPRL) is reached. This combination seems to be the best solution for properly setting the record level. I will probably have to buy a new deck within two years, but feel threatened by the ever-changing technology. There appears to be a trend to eliminate VU meters in favor of LED displays. By far I prefer the simple and reliable VU meter, despite salesmen's attempts to convince me that the new devices are ultra-superior. There seems to be greater chance of malfunction with an array of lights than with a simple meter. My question is whether tape decks in the near future will phase out VU meters altogether, or whether the industry will give the consumer a choice.

-Marshall Saiger, Long Beach, Cal.

A. I really can't guess what the home tape deck industry will do in its quest for new gadgets to promote sales. Nor can I guess which existing or future gadgets will prove superior to the devices they supplant. Nonetheless, I am inclined to feel, much as you do, that a VU meter plus a lamp that lights on MPRL--or else a peak-reading meter-affords an excellent way of steering between the Scylla of distortion produced by too high a recording level and the Charybdis of noise resulting from too low a level.

In the beginning, most home tape decks used an "electronic eye," a fluorescent tube with a V-shaped shadow that closed at MPRL. This was very easy to use, reliable, and conducive to good results in recording. Its drawback, felt probably by only a minority of home recordists, was that it did not provide a numeric indication of relative levels in dB below (or above) MPRL. To give a professional look, home decks then introduced so-called VU meters. In many cases-quite likely most-the chief characteristic of these meters was that they wiggled; seldom did they have the response and decay time characteristics, and the frequency response, of true VU meters. But as time went by, the situation improved; true VU meters or meters with traits quite similar to them appeared more frequently.

Then there was a return to peak reading devices, such as the electron is eye, but in different forms. One way was to substitute a peak-reading meter for an average-reading (true) VU meter. Another was to make the meter switchable between average-reading and peak-reading. Still another was to add an LED or other device that would light up when MPRL was reached.

(About here it is appropriate to slip in a note that European professionals have long used peak-reading meters, in contrast to American professionals, who have long used average-reading meters.)

The most recent stage has been to use a succession of LEDs or a fluorescent bar (bar graph); these devices have the virtues of accurately following signal peaks and of indicating relative level. As to their reliability-freedom from failure-compared with the meter, as yet I have no information. I suspect that the indicator comprising a string of LEDs is apt to be the first to go.

Where do we go from here? I dunno. Anything is possible, including voice announcements, a flag that rises and falls with record level setting, smoke signals, etc. We might even return to meters.

Azimuth Problem

Q. I trade tapes, and nearly all the ones I receive are out of phase due to being recorded and played back on different decks. My equipment is checked regularly, so there is nothing wrong on my end. Is there an outboard device I can buy to adjust the phase of such tapes for better frequency response?

-David White, San Jose, Cal.

A. Your problem is one of azimuth, which of course introduces phase shift and treble loss. Correct azimuth alignment of a tape head requires that its gap be at a right angle to the long dimension of the tape. An azimuth error in recording can be compensated by an identical error in playback. Thus, if a deck uses the same head for recording and playback, or if it has separate heads but with equal azimuth errors, there will be no treble loss due to azimuth misalignment. In your case, it is not necessarily true that your head or heads are in correct azimuth alignment; you may simply have matching errors. On the other hand, your heads may be correctly aligned, with the fault lying in the decks of others.

I know of no device such as you are seeking. The closest thing is Nakamichi's expensive Dragon tape deck, which automatically adjusts azimuth in playback for maximum treble response. It does so by comparing phase at the top and bottom of a track; adjustment is continuous during playback.

(Audio magazine, Feb. 1984, HERMAN BURSTEIN)

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