Tape Guide (Oct. 1977)

Multiple Taping

Q. I have a 250-watt amplifier with a single input and output and am therefore only able to accommodate one tape deck. I would like to connect this to two tape decks, enabling me to record with either deck, or to play back from either deck without having to swap leads. Would it be possible to use simple "Y" connectors?

-Albert Emrich, Dover, Del.

A. Frequently "Y" connectors will do the job you describe without the two tape machines interfering with each other. If there is interference, putting resistance on the order of several hundred to several thousand ohms in series with each hot lead may solve the problem. Another solution is to build your own switching system that simply switches the amplifier output between the hot lead inputs of decks A and B; and similarly for playback. Visit local audio dealers and look at commercial switch boxes which are intended for purposes like yours, such as the Russound TMS-1W or Sony's SB-300.

Multi-Track Conversion

Q. I have an Ampex Model FR-100 seven-track instrumentation tape transport which I plan to convert into a seven-track audio recorder. I would like to be able to erase any single track without disturbing the others, but the deck only has record and play head stacks. Would it be possible to use one of the head stacks for erasure?

- James Kobs, Albuquerque, N.M.

A. I doubt that it is feasible to use either a play head or a record head for erasure. If you try to drive enough high frequency current through the head to achieve satisfactory erasure, you may burn out the head. However, if I am wrong, the head which seems most likely of doing this job would be the record head.

Tape Deck Hookup

Q. Which is the best way to play a tape deck connected to a receiver: (a) Set the volume control on the receiver so you have a normal listening level for FM reception, then adjust the playback control on the tape deck to have the same listening level when playing tape? (b) Set the playback control on the tape deck to its maximum position, then adjust the volume control on the receiver until an agreeable listening level is reached? (c) Adjust the playback control on the tape deck to have a 0 VU reading on the loudest passages, then adjust the volume control on the receiver until an agreeable listening level is reached?

-William Lawrence, APO, San Francisco.

A. I think that method (a) is at least as good as the other two methods and perhaps better. It would tend to avoid the possibility of overloading your receiver, unless the high level signal fed to the receiver goes directly to the volume control. I don't think that a 0 VU reading on playback would have much significance for a home receiver, although it might for a professional piece of equipment where it is essential to know absolute signal level.

Dropouts

Q. My Sony TC-230 tape recorder has a problem with dropouts. During playback of a tape, one or both channels suddenly suffer a complete loss of signal or a dramatic reduction in output which usually lasts only a fraction of a second. This does not occur when I monitor the input signal, nor does it occur when playing tapes recorded on other machines, or when playing records through the amplifier of the tape deck. I guess this narrows it down to the recording process.

-Howard Sanner Jr., Hyattsville, Md.

A. Your analysis seems correct. A possible cause is a fault in the bias oscillator circuit which would cause it to stop momentarily or to drop in amplitude. However, this problem seems unlikely since the erase head would also quit and you would hear the previously recorded signal for a fraction of a second, unless you were using virgin or bulk-erased tape.

Another possibility is that you are recording at such a high level that momentary blocking occurs in the record amplifier. This could happen if the sound source contains high frequencies of substantial amplitude which are then subjected to substantial treble boost in the record amplifier. This could also be due to a poorly soldered connection. Finally, you might have an erratic capacitor, resistor, or transistor in the record circuit. Signal tracing would be necessary to find the point where this problem arises in the record amplifier.

Head Replacement

Q. I wish to replace the heads on my KLH 41 tape deck. Please don't say "ship it to an authorized service center" because, despite the risks involved, I'd much rather do the job myself. Could you tell me which head design would require the least modification to the KLH circuitry, what these modifications would be, what kind of equipment I might need, and what kind of parameters I should measure in the original heads to help me find a suitable replacement

- Kurt Wiley, Rochester, N.Y.

A. I think you should try to get most of this information from a manufacturer of replacement heads, such as Nortronics. They can tell you which heads of theirs are most compatible with your machine and what changes, if any, are needed. The head parameter of dominant importance is impedance at a specified frequency, e.g. 1,000 Hz. Of course, head format is also important, that is whether the head is half-track, quarter-track, etc.

In using a new record head you will probably have to adjust, or at least check, the bias current. Appropriate changes may also be necessary in the amount of signal current supplied to the record head and in the calibration of the record level indicator. Change may be required in the current supplied to the erase head. Perhaps, a slight change may be needed in playback equalization, although this is the least likely possibility. To make all these necessary changes you will need a signal generator going over 100,000 kHz, a VTVM, and an harmonic distortion tester, in addition to a test tape for azimuth alignment and to check the playback response.

(Audio magazine, Oct. 1977; Herman Burstein)

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