Tape Guide (Q and A) (Aug. 1976)

Reverse Delay

Q. The reverse mechanism of my Concord Mark IV auto-reverse tape deck is triggered by sensing the no signal period at the end of the tape.

The reversing mechanism has a built-in time delay of 7-8 seconds to preclude reversal in the middle of a selection. I find this delay to be insufficient and would like to know if the delay can be increased to 11-12 seconds. Would this be a complex and/or costly adjustment and perhaps one that I could perform myself?

-David Wilson, Newton, Mass.

A. I don't think the change would be difficult. Probably it only involves changing the value of a resistor and/or capacitor in order to obtain a greater time constant. When you locate the time-delay circuit, try experimentally increasing its capacitor by about 50 per cent.

Background Noise

Q. (1) When my Roberts 770X tape recorder is on, 1 can hear broadcast stations in the background. What can I do about this? (2) How may I record from my mono cassette into the Roberts and vice versa? (3) What part of my Roberts recorder should I connect to for ground? Should it be grounded to the a.c. outlet or the amplifier ground terminal? I already have my tuner and phono turntable grounded to the amplifier terminal. (4) I want to put conversation on the tape at the same time that I am recording it. How may this be done? (5) In recording from FM and discs, what should be the tone control settings?

-Tommy Allen, Highland Park, Mich.

A. (1) Try a small capacitor (up to about 50 pF) between the first stage input and ground. (2) If your cassette does not have an output jack, take the output signal from across the playback gain control. Take your cassette machine to your local audio store to ascertain what connecting cables and plugs you will require for input and output. (3) I surmise you have a hum problem and have found that grounding helps overcome it. Any screw in the tape recorder chassis would provide a ground. But one often finds experimentally that some grounding points do a better job of reducing hum than others. Your tape recorder is already grounded to the amplifier via the connecting cable. If you are going to run a separate ground from the tape machine to the amplifiers, this might increase hum. If a separate ground from the tape machine to the amplifier doesn't help, then try connecting the ground to the a.c. outlet (earth) ground. (4) If your tape recorder does not already provide mixing facilities, you will have to acquire a separate mixer in order to combine input sources. (5) Adjust the tone controls according to what your ears prefer. The settings should ordinarily be electrically flat, unless you are trying to compensate for some unbalance in the source material.

Cassette Changes

Q. For a long time I have been using Scotch C-90 and C-120 cassettes with very good results, but I have had difficulty with them. Upon playback I have found the recording to be fuzzy.

Going back to my older cassettes, I obtained the usual good results, confirming that my recorder is not at fault. Thinking that the new C-90s and C-120s might be part of a bad run, I purchased more of these, but the recordings turned out just as badly.

-F. S. Kemp, Sterling, Conn.

A. You may be getting new tape formulations under the old label, perhaps requiring different bias and equalization. In an effort to make the cassette competitive with open reel, there have been rapid developments in tape formulation. Fuzziness may be due to the fact that your machine provides insufficient bias for the newer tape.

(Audio magazine, Herman Burstein)

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