Tape Guide (Jun. 1982)

Save Tape and Time?

Q. Using a pickup, preamp, and tape deck with very good high-frequency response, and using a variable speed turntable, how much degradation would I get if I do the following: (1) Adjust the turntable speed for 66 2/3 rpm, (2) record a high-quality tape at 7 1/2 ips, and (3) play the tape at 3 3/4 ips? This would save half the duplicating time and half the tape.

-T. Bainbridge, Milwaukee, Wisc.

A. Your procedure would involve doubling all frequencies on the phono disc so that, for example, 15 kHz becomes 30 kHz. Therefore, one question which arises is whether the record electronics of the tape deck can handle frequencies this high without significant loss. Another problem is that of record equalization, which would have to cater to frequencies going out to, say, 30 kHz instead of 15 kHz. Optimum bias might also vary; so might optimum bias frequency, because the chance of the oscillator frequency beating with audio frequencies would be increased. The only real way to find out how well (or poorly) your proposal works is to try it. From a practical standpoint, despite theoretical difficulties, it might work satisfactorily, but you would not save on tape. In recording at 7 1/2 ips you are using twice as much tape as you normally would for a playing speed of 3 3/4 ips. In playback at 3 3/4 ips, you are using half as much tape as you normally would for a recording speed of 7 1/2 ips; hence you break even.

Self-Service

Q. Having been interested in tape recording for some time, I've become increasingly accustomed to doing my own servicing on my tape decks. Is there a good complete manual or book on how to do all of the necessary alignments and adjustments of the electronics of tape recorders? I would like to know how to go about setting up the correct bias, equalization, etc. Also, please recommend open-reel test tapes.

-Bill Lewis; Bakersfield, Cal.

A. I do not know of a single manual or book that will adequately cover service and alignment procedures for all, or most, or many tape decks. The way to acquire knowledge and competence in this respect is to struggle with the manuals and procedures for a variety of decks until you discover what procedures they have in common and what procedures are unique to particular decks. Some of them, such as checking frequency response, will tend to be much the same, while others, such as adjusting bias and/or equalization, will tend to vary considerably. (Editor's Note: Howard A. Roberson's article, "Tape Recorder Maintenance," Audio, April 1982, p. 32, may help in this area.) With respect to test tapes, I suggest that you write to (1) Ampex, 2201 Lunt Ave., Elk Grove Village, III. 60007; (2) Taber Manufacturing and Engineering, 2081 Edison Ave., San Leandro, Cal. 94577; (3) Magnetic Reference Laboratory, 999. Commercial St., Palo Alto, Cal. 94303; (4) Nortronics, 8101 West 10th Ave. North, Minneapolis, Minn. 55427, and (5) Audiotex, 400 South Wyman, Rockford, Ill. 61101.

Once, 1/2, or 1/4 Around the Track

Q. What is the difference between full-track, half-track, and quarter-track recording when using an open-reel deck? Does full-track recording have an advantage over the others?

-R. Watson, Dover, Del.

A. Half-track recording uses a little less than half the tape width to record each of two tracks, which are separated by a small space called an island.

Half-track permits recording either a pair of stereo signals in one direction of tape travel, or a mono signal in both directions. Specifically, in mono you record a signal on the upper portion of the tape and then reverse the reels and record on the lower portion (when the reels are reversed and turned upside down, what was originally the lower portion becomes the upper portion to be recorded).

Quarter-track recording uses a bit less than one-quarter of the tape width to record each of four tracks, separated by three islands. This permits (1) recording a pair of stereo signals first in one direction of tape travel and then a pair in the opposite direction, (2) recording a set of four quadraphonic signals in one direction of tape travel, or (3) recording four mono signals, entailing three reversals of the tape reels.

If the four tracks are numbered 1 through 4, starting from the top, the first pair of stereo signals is recorded on tracks 1 and 3, and the second pair on tracks 2 and 4. Track 1 and track 4 are the left-channel tracks. Most decks offer only the first and third options listed above, while some offer the first option only.

Full-track recording occupies the entire tape width and permits only the recording of a mono signal in one direction of tape operation. The wider the track, the higher the signal-to-noise ratio, if everything else remains the same. Thus, full-track recording provides about 6 to 8 dB better S/N than quarter-track. On the other hand, the narrower the track, the less the reduction in treble response due to azimuth misalignment.

Why Elcaset?

Q. I own an open-reel deck, a fine cassette deck, and now I plan to purchase an Elcaset deck. It seems that this format is equivalent to the open reel format but without the bother. I would like to know why it did not do well when it came out a few years ago, and if it will come into production again.

-Michael Jamet, Bronx, N.Y.

A. Although there is an occasional rumor that the Elcaset format will be resurrected, majority opinion is that Elcaset is dead, and, in my view, rightfully so.

In light of continuing improvements in cassette tapes, in the heads available for cassette decks, in deck electronics, etc., the advantage of Elcaset became marginal. Further, Elcaset presented one format too many to a consumer already beset by: Open reel, cassette, and cartridge formats; a variety of reel sizes and speeds in the open-reel format; a variety of tapes, with varying bias requirements, record equalization, and playback equalization; a variety of noise-reduction devices, and probably other variants have forgotten to mention.

Returning to the basic explanation: Today the state of the cassette art permits essentially flat response from about 20 Hz to 24 kHz with signal-to-noise ratio of about 70 dB (using Dolby C) and with low distortion and very low wow and flutter. While only the finest and most expensive cassette decks achieve such performance today, the pack is not all that far behind. And there is no sign that continued improvements will fail to materialize, so that the pack tomorrow will be where the leaders are today. Therefore, why Elcaset?

Clean but Soundless

Q. I recently purchased a combination head cleaner and demagnetizer cassette. The instructions state that a few drops of the fluid cleaner should be inserted in the open part of the cassette device. After following the instructions and going through a record-play run with this cassette, I heard no recorded sound during playback. When I try to play tapes that I recorded prior to use of the cleaner demagnetizer cassette, the sound is muffled and dull. Have I done permanent damage to the tape heads? I rue the day that I bought this cassette.

-Donald McHugh, Brooklyn, N.Y.

A. It is not certain that the heads have been ruined. Possibly the fluid, in combination with tape oxide, has coated the heads and made them inoperative because of excessive tape-to head separation. Perhaps a careful cleaning in the conventional manner will restore the heads to correct operation. Unless your instruction manual indicates otherwise, apply isopropyl alcohol on a cotton swab to clean the heads, capstan, and pressure roller.

Allow at least five minutes for everything to dry before checking your deck with a new cassette.

It is possible that the heads are okay but that the fluid leaked inside your deck and did some kind of damage.

Another, but very small, possibility is that by coincidence you used the cassette device just at the time when a totally unrelated problem developed in your cassette deck.

Helpful Humidity

Q. My house is quite dry in winter, with a troublesome accumulation of dust. If I used a humidifier to cut down on the dust, would the moisture have any effect on my stereo equipment?

-Michael Lemieux, Rouses Point, N.Y.

A. Assuming that you do not allow the humidity to go much above normal level, I doubt that use of the humidifier will adversely affect your audio system. In fact, it may be beneficial with respect to tape deck performance, preventing the tape from becoming so dry as to cause squeal.

If you have a problem or question on tape recording, write to Mr. Herman Burstein at AUDIO, 1515 Broadway, New York, N.Y. 10036. All letters are answered. Please enclose a stamped, self-addressed envelope.

(adapted from Audio magazine, Jun. 1982; HERMAN BURSTEIN)

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