Tape Guide (Q and A) (Nov. 1972)

Phones For Monitoring

Q. I have a TEAC tape deck, model A-1200-U. To make use of the tape or source monitoring feature, headphones of 10,000 ohms impedance or better are required. The dealer whom I purchased the tape deck tells me that high fidelity phones are not made in this impedance range. I wrote to TEAC asking. if they could suggest a source of supply for the required headphones, and they have not replied. I want to use the TEAC for recording without disturbing others in the room, and I am afraid to use my present 4-16 ohm phones for fear of overloading the outputs of the TEAC. Any suggestions you may have will be gratefully received.

-J. Francis Hartmann, Glen Ellyn, Ill.

A. You might write directly to headphone manufacturers for suggestions.

Perhaps you can do something like the following. Connect the low-impedance (presumably high quality) headphones you have to the output of the power amplifier, and work out a switching arrangement that disconnects the speakers from the power amplifier.

Since there should always be a load across the output of the power amplifier, either the switching arrangement should substitute a dummy load resistor, or you should leave a dummy load resistor (about 30 to 50 ohms) permanently connected to the output of the power amplifier. The resistors in question should be rated at 10 watts or more.

Low Playback Level

Q. I experience a drastic reduction in signal level during playback after a recording. (I am not recording at too low a level inasmuch as prerecorded tapes give me about the same playback level as tapes I have recorded) If the volume control is set at 2 when monitoring the source, then it has to be moved to about 5 or 6 when monitoring the tape playback in order to get the same level. I will be grateful for any light you can shed on this problem.

- Kohoh Ansah, New York, N.Y.

A. Your problem in brief is that the playback level is substantially lower than the monitoring level. The fault lies either in the design of your tape recorder or in the misadjustment of an internal control (if there is such a control) which permits the playback and monitoring levels equated.

Further, keep in mind that for the same signal level applied to the tape, some tapes have higher output than do other tapes. Accordingly, if your machine contains a control of the type I have mentioned, it has to be set on the basis of the tape you are using.

Cassette vs Reel Recorders

Q. I have a mono open reel tape recorder. I am thinking of purchasing a stereo recorder. However, some people feel a cassette is better for what I want to use this machine for, mainly taping radio and TV programs. What do you advise? How would one connect the cassette to the radio or TV for recording?

-Sam Gerfinkel, Yonkers, N.Y.

A. For high quality reproduction you are probably better off with an open-reel machine. However, a cassette machine offers you a much more compact device. If you are planning to record mainly from radio (presumably mono) and TV (mono of course), I don't see why you want a stereo recorder. If the radio or TV has a tape output jack, you would connect this to the high-level input of your tape machine. If they lack such a jack, you can obtain the signal across the volume control of either unit. Third, but least desirable, you can obtain the signal across the speaker leads of the radio or TV. If you take the signal across the volume control, keep the cable from the unit to the tape recorder as short as possible and of minimum capacitance per foot.

Background Noise

Q. When I use my Ampex 601 in recording from FM station WNCN, during the playback of that program there is an annoying background noise that is present neither in the original broadcast nor in monitoring. What could cause it, and how can I eliminate it? Strangely, WNCN seems to be the only offender.

-William E. Hlad, Bronx, N.Y.

A. Possibly, very high frequencies--too high to be initially audible-are beating with the bias frequency of your tape recorder to produce audible noise. For example, harmonics of the multiplex 19,000 Hz signal could be doing this. In such a case the solution may be to insert a high frequency filter (cutting off sharply above 15,000 Hz) between the output of the FM tuner and the input of the tape recorder. Consult your audio dealer about such filter.

Mono Recording

Q. Regarding the use of a mono open reel tape recorder to record from a stereo radio: (1) Do I control recording volume with the volume control of the radio or with the volume control of the tape recorder? (2) Since the recorder is mono, should I use only one channel of the stereo radio? (3) To feed the tape recorder I use a patch cord with alligator clips. Is the best hookup to the speaker terminals inside the set or to the two screws in back of the set that are attached to the speakers?

-Sam Gerfinkel, Yonkers, N.Y.

A. Adjust the recording level of your tape machine by means of its volume control. Once you have found the proper setting for this control, do not change it while recording. Your tape recorder should be connected to the combined output of both channels. Otherwise you will not pick up all the program material. If your radio has a stereo defeat switch, this will supply a combined output in the defeat position. If it doesn't, you might try the following.

Connect two resistors in series, each of about 16 ohms and two watts rating, between the hot terminals for each speaker. Connect your patch cord to (1) the midpoint of these two resistors and (2) ground. It doesn't matter whether connection is made to the speaker terminals inside the set or to the screws leading to the speakers.

Input Matching

Q. I have a tape deck whose output is 1 volt. I plan to buy an audio receiver with an input sensitivity of 170 mv. Would this receiver match my tape deck?

-George S. Hatch, Jr., APO.

A. The two should match well. The receiver requires a minimum of 170 mV and can probably accept a few volts before overloading. The 1 volt output of your tape deck fits well within this range.

(Audio magazine, Nov. 1972; Herman Burstein)

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