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

Open-Reel or Dolby Cassette?

Q. I'm planning to purchase my first tape recorder, which I1 will use to build up a tape library. I can't decide whether to get an open-reel deck or a cassette deck which includes Dolby noise reduction. Some people tell me that the open-reel machines have lower wow and flutter, less distortion, and wider frequency response, and that I can always add Dolby to any machine later. Others claim that cassette decks using Dolby and chromium dioxide tape can have just as good frequency response, equally low distortion, and wow and flutter as good as most open-reel decks (except those with three separate motors, which cost a lot more). In addition, of course, there's the convenience of cassettes.

I've also heard that cassette will replace discs before long. Which is most likely to be around longest, and which will offer the best fidelity?

-Stephen P. Sherman, West Hartford, Conn.

For years people have been repeating stories that tape would largely outmode the phonograph disc, but discs are as strong as ever. Similarly I doubt that cassettes will drive out the open-reel decks in the forseeable future. As for chromium tape, it does make more improvement in cassettes, with their 1-7/8 ips speed, than in open-reel decks running at 7 1/2 ips, because the open-reel at the speed doesn't need chrome tape. Even though cassettes are very good, the best open-reel machines are better.

Too, there's more recording headroom with open-reel, so you can make recordings more reliably with open-reel than with cassettes.

Wants to Replace Heads

Q. About five years ago 1 purchased the Norelco Continental 401 four-track tape recorder. When I checked on replacement heads and transport components at North American Philips, I learned that my machine has been discontinued. Can you advise on the feasibility of a separate transport to be used with my existing electronics, or is this impossible, unreasonable, or just not worthwhile?

-Robert J. Galligan, Niantic, Conn.

A. I don't know of any separately available transports. If a surplus mechanism such as is sometimes offered in the classified pages were purchased, you'd have some job matching it with the electronics for equalization, audio record current, bias current, erase current, and calibration of the record level meters. I don't think it's a practical idea. However, you can get replacement heads for just about any tape recorder ever made by writing to Nortronics Co., Inc., 8101 W. 10th Ave. North, Minneapolis, MN. 55427.

Cassette Production

Q. Who manufactures tape machines that will take a master tape and produce a number of cassette copies?

-Frank J. McDonald, Baldwin, N.Y.

A. I suggest that you query the following companies which are involved in tape duplication:

(1) Ampex Corp., 401 Broadway, Redwood City, CA., 94063.

(2) Sony Corp. of America, 9 West 57th St., New York, N.Y. 10019.

(3) Telex Communications, Inc., 9600 Aldrich Ave., S., Minneapolis, Minn. 54420.

Recording Troubles

Q. I have a problem with my Ampex 1100. After taping a selection from a record, I play back the tape and find that the left channel decreases in volume and the high frequencies fade into the background in many places on the tape. This happens at the same place every time I play the tape. I have tried to re-tape the selections several times, and the problem occurs in different places along the tape (but not throughout the entire tape). The volume comes back to normal after a few seconds, and then it decreases again. I keep the heads demagnetized and cleaned. I also have trouble when I want to record a reverse signal. It doesn't record all the time, and when it is on the tape it doesn't always activate the reverse mechanism.

-Eva Barkovich, Detroit, Mich.

A. I suspect that your difficulty is what is known as left-channel dropout and is due to inadequate contact between the tape and the upper gap of the head, in your case, the record head. The reason for inadequate contact may lie in the tape guides, in tape tension exerted by the supply and takeup reels or in the nature of the tape path. Another possibility is a fault in the record electronics, causing the audio signal to wax and wane. Your problems calls for the services of a qualified technician.

Deck-to-Deck Hookup

Q. In my hobby of creating electronic music 1 use two tape recorders, a Harman-Kardon TD-3, which has three heads, and a Realistic 300-D, which has two heads. With the Realistic I can record on one channel while listening to the other. However, using the Harmon-Kardon, this is not practical because the playback head is separate from the record head, causing the channels to be out of timing when played back. Is it possible to route the wires which lead to the heads to a switching panel so that either channel of either head could be operated in the playback or record mode independently of the other channels? If this is possible, what problems would there be?

-Bruce R. Gerow, Liverpool, N.Y.

A. If you wish to use the same record head for either recording or for playback, and the same for the playback head, the likelihood you'll run into trouble is great. Usually the record and playback heads are of different design to optimize the performance of each. Consequently each head has different impedance and gap width. However, you could use your switching scheme if you can sacrifice treble response while monitoring. Another idea is to substitute a new playback head for the record head, but this requires adjusting the bias current, the audio record current, and calibrating the record level indicators.

Surplus Tape Transport

Q. I have acquired a tape transport that was originally part of a computer tape memory. The unit was manufactured by Ampex and is in such good condition that I would like to convert it to an audio machine. I would like to know whether or not the flutter and wow of this type of machine is low enough to make such a conversion possible. The capstan motor is a hysteresis motor, which is fine, but the spooling motors are d.c. units and are switched off and on by two tensioning arms. There is also a vacuum loop that I would like to remove.

Also, what speed does this machine operate at normally, and are the present heads in the machine any good for audio purposes?

-Alan Hoffman, Lyndhurst, Ohio.

A. My guess is that the motion characteristics of your tape transport are excellent. I have no information about the speed and head characteristics. This kind of information must be sought from the manufacturer, (The speed is likely to be much too fast-computer tapes usually run at 100 or 200 ips). The heads are 1/2 inch wide, and not suitable for audio use.

A skilled development technician could convert such a deck into a good four- or eight-track audio machine, but it would take a great deal of research and design effort. It's unlikely that a tape enthusiast could successfully complete such a project.

AM Radio Interference

Q. I own an Astrocom/Marlux 407 deck. During the daytime when AM stations broadcast, their signals are picked up by my tape deck. I have this trouble only in playback mode because recordings made at the same time don't have the radio signals mixed in. I tried grounding the front panel of the tape transport section to my amplifier chassis and the noise was cut down a little, but it still is noticeable. What can I do?

-John F. Wood, Huntsville, Ala.

A. The first amplifying stage of your playback preamplifier has very high gain and is picking up the radio signals, rectifying them at the same time that it amplifies them. Sometimes the problem can be eliminated by placing a small capacitor at the input of the first amplifier stage. Experiment to see what the smallest value capacitor is which will kill the undesired signal.

Often something between 10 and 50 pF will do the job. If this fails, you will have to experiment with extra shielding of various parts of your system, possibly grounding it (and the entire system) to a water pipe or other good earth connection.

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

= = = =