Tape Guide (Q and A) (Aug. 1975)

Tape Head Care

Q. I am writing to you in the hope that you will be able to answer questions that my dealer can't. I am the proud owner of a Revox A-77 deck.

The manual supplied with the machine is very comprehensive, but it makes no mention of routine head and guide demagnetization. Is such maintenance required for the A-77?

Also, my machine is set up for Scotch 203 tape. Will the use of a thicker base tape (1 1/2 mil Scotch 202) cause any significant increase in head wear?

-Peter A. Thrift; Bellevue, Nebraska

A. Manufacturers often recommend that heads and guides be demagnetized after about every eight hours of use. On the other hand, at least one manufacturer recommends much less frequent demagnetization.

If you want to be on the safe side, I suggest that you write to Revox.

I doubt that there will be significant difference in head wear according to the thickness of the tape. More important is the quality of the tape you use. One that is optimally lubricated and that doesn't shed excessively is best. Tape tension and pressure exerted by pressure pads (is used) also affect in head wear.

Which Tape Deck to Buy?

Q. I am trying to decide which tape deck to buy. I want no compromises. I want it to have 10 1/2-in. reels, three motors, solenoid operation, automatic stop at predetermined places, auto-reverse, smooth handling, 15, 7 1/2, and 3 3/4 ips speeds. I have read that the only difference between a quarter-track and a half-track recording is about 3-dB better signal-to-noise ratio. Is this true, and how much difference does 3 dB make?

I have read a lot about the Dolby system and wonder if it would provide much improvement on a top-quality recorder? I am listing the machines I am considering. Please tell me which are the best, and also what tapes are the best.

-John Nuss, Old Bethpage, N.Y.

A. I cannot make recommendations as to the best machine for your needs. As I have stated here previously, Audio's policy prevents me from doing so. Considering the high standards you are setting for yourself and the considerable amount of money you will be spending, I believe you should take the time to get out to the audio stores to check with your eyes and ears the performance of the machines which interest you.

A 3-dB difference in signal-to-noise ratio is significant, but barely so. In other words, it would be slightly audible. With fine tape machines such as those you list I doubt that Dolby would make much difference audibly, unless you go down to the slowest speeds. Dolby makes the most improvement with machines which have poor S/N ratio to begin with.

Correcting Wandering Tape Speed

Q. When I listen to a tape from my mother made in 1964 on a small, cheap reel-type "voice letter" machine, the speed varies throughout the tape, and her voice runs from a squeaky high to a low bass. I have dozens of tapes kept over the years, some with voices that no longer exist, and others which can never be duplicated. All contain some speed variations. Is any equipment available that I can use to correct the speed of these tapes while I make new, even speed copes of them?

-J.R. Kendrick, Honolulu, Hawaii

A. The only solution is to vary the frequency of the a.c. power to which you connect your tape machine. You can build such a power supply from construction articles which have appeared from time to time in electronics magazines. Or you can use an audio oscillator connected to a power amplifier and vary the sine wave output of the power amplifier, using it to supply the a.c. power for your playback tape machine. Of course, the machine you make the new recordings on will use regular a.c. power.

Recording Whistle

Q. For years I have been recording off the air with an Eico RP100 recorder and a Scott 350B tuner with satisfactory results. I recently acquired a new tuner, Kenwood KT6000, and with the same recorder I now get a continuous high-frequency whistle along with the program material. I am told this is due to interaction of the bias oscillator of the recorder (50-100 kHz) with the pilot tone (38 kHz) that is part of all stereo broadcast signals. How can this be corrected?

-Stephen Gaydica, Hewlett, N.Y.

A. The reason you have been given is probably correct. The solution is to introduce a tunable filter between the tuner and the tape recorder. I suggest that you consult your local audio store, a mail order audio house or the makers of your equipment.

Recording Level Problems

Q. I am recording with a TEAC A15000 tape deck. I set the monitor switch to Source and adjust the level so that the VU meter reads 0 on the loudest passages. When the tape is played back, the level is too low (hiss is audible), and peak passages register only -4 or -5 on the VU meter. I have played my tapes on another deck (Sony 255) and get the same low playback level. But a tape recorded on the Sony plays back properly on the TEAC. I am using Scotch 290 (1/2 mil) tape.

-John L. Bagwell, Lanham, Maryland.

A. It appears that your problem is mis-calibration of the VU meter. Whether this is true for tape in general, or only when you use 1/2 mil tape, can easily be checked by investing in a small reel of 1 1/2 or 1 mil tape and noting whether you still get under-recording. It is also possible that your machine is under-biased. Up to a point more bias current increases the amount of signal that gets recorded on the tape. If treble response is exaggerated, which can happen when there is too little bias, then under biasing is indicated. Have an authorized technician check the bias and record/play response.

Concert Hall Recording

Q. I have the fantastic opportunity of recording live in the Teatro Colon, in Buenos Aires, one of the best concert halls in the world. The Teatro Colon, however, does not encourage recording engineers, and its equipment is painfully obsolete. I must get acquainted with modern equipment and techniques for recording live, but none of the magazines to which l am a regular subscriber offers much information on recording techniques and equipment. Would you know of any publication (books, manuals, magazines, catalogues, anything!) that could give me not-too-technical reports on available recording equipment and general information about recording techniques?

-Oscar J. Romero; Buenos Aires, Argentina

A. You might write directly to manufacturers of recording equipment. You can get their names and addresses from Audio and other periodicals in which they advertise.

Audio published a series of three articles by David Josephson on Microphones in December, 1973, July and Aug. 1974. You will find a chapter on microphones in Hi-Fi Made Easy by Norman Crowhurst (Gernsback Library, 154 W. 14th St., New York, N.Y.). A chapter on microphones is in my book, Getting the Most Out Of Your Tape Recorder (John F. Rider, Inc., 114 W. 14th St., New York, N.Y.) A chapter on using a tape recorder and microphones ("Increase Your Enjoyment of Music") is in How To Select and Use Your Tape Recorder by David Mark (Rider). And a chapter on stereo microphone technique is in my book Stereo, How It Works (Gernsback).

(adapted from Audio magazine, Aug. 1975; Herman Burstein)

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