Tape Guide (Q and A) (May 1970)

Recorder Connections

Q. I own a ° ° ° ° tape recorder and use it with a stereo receiver. When I connect the tape-output jacks of the receiver to the line-input jacks of the tape recorder, the recorder works correctly, and only monitors the receiver signal when in the record mode. When I connect the line-output jacks of the tape recorder to the tape monitor jacks of the receiver, it also works correctly. But the other day I accidentally connected the tape-output jacks of the receiver to the line output jacks of the tape recorder, and was quite startled by the results. My tape recorder monitored the receiver signal only in the "play" mode, and the incoming signal was not affected by the recorder's volume or tone controls, and the VU meters of the tape recorder did not register. When in the record mode, the recorder worked normally and did not register an incoming signal unless one was fed into the line input jacks. Is this normal, or did I inadvertently damage my tape recorder?

-Bruce Schwartz, Philadelphia, Pa.

A. First of all, it is highly unlikely that you damaged your tape recorder. Your description of what happened, so far as I can follow it, seems to be what one would normally expect for a misconnection such as you made.

For a more precise reaction, I would need schematics of your tape machine and receiver, together with a more detailed and clearer description of exactly what happened.

Hysteresis Motors--And Hiss

Q. Is the hysteresis-synchronous motor an especially desirable feature? Will a frequency response to 20 kHz introduce an objectionable amount of hiss?

-A. L. Bowling Jr., Lynchburg, Virginia.

A. A hysteresis motor to drive the capstan is desirable in the interest of accurate tape speed and uniform speed from one end of the reel to the other.

I doubt that frequency response to about 20 kHz, provided this is essentially flat response, will add significant hiss when compared, say, with a response to about 15 kHz. Hiss is most apparent to the ear in the region of about 3 kHz to 5 kHz.

Overloading

Q. How can I check if the recording amplifier of my tape machine is overloading before the tape is saturated? I have access to an oscilloscope, VTVM, harmonic distortion analyzer, signal generators, and VOM.

-Seitoku Nashiro, Arlington, Virginia.

A. Record and play back a mid frequency signal of about 400 Hz.

Monitor the tape playback on the 'scope. Keep increasing the level of the recorded signal until the 'scope shows a distorted waveform. Now check the waveform at the output of' the recording amplifier (at the input to the record head) ; if it looks undistorted, you are not overloading the amplifier.

Endless Loops

Q. I wish to use a tape recorder as an aid in my musical instrument lessons. My instructor would record a passage, ranging from 30 seconds to several minutes. I would play along during playback of the tape. The recorded passage should repeat endlessly, without requiring my instructor to record the same passage more than once. How can I achieve this?

-D. Menkes, Westmont, New Jersey.

A. By borrowing a second tape recorder (say from a friend), you can copy the original recording over and over through the length of a reel. If you purchase a tape recorder with automatic reverse in both directions, you can play such a tape endlessly.

VU Meters

Q. I made the mistake of advancing the output level too far on each channel of my tape recorder, and pegged the VU meters. Could the meters be damaged in this manner?

-John D. Moss, Aartselle, Alabama.

A. If the meters are true VU meters, they can take a very substantial overload without damage. They can continuously withstand a voltage 5 times as great as that which is required to drive them to a reading of 0 VU. And they can withstand for 1/2 second a ten-fold voltage overload. If they are not true VU meters, it is anyone's guess what might have happened to them as the result of pegging. The chances are that the manufacturer of a high-quality tape machine would use meters of comparable quality that can withstand pegging within the capabilities of the machine's amplifiers.

One way that you might be able to tell if the meters have been affected is to feed in a steady signal while recording, and see whether they give the same reading in both vertical and horizontal position. If they do give the same reading in both positions, quite likely they have not been harmed. Also see whether the same signal produces the same reading on the two meters; it should.

Bias Adjustment

Q. I own a ° ° ° ° tape deck and wish to adjust bias for optimum performance with the tape I am using. I plan to adjust bias to peak and output level while recording a 1600-Hz sine wave.

-Ronald Brey, Mankato, Minnesota.

A. The procedure you describe is approximately the one generally used and apt to give optimum or close to optimum results. However, you might try increasing the bias until output drops about 1 dB below peak output. If this does not cause undue treble loss (say no more than 2 or 3 dB loss at 15,000 Hz at 7.5 ips), then it is a desirable adjustment of bias; it results in less distortion and in less susceptibility of treble response to slight changes in bias current (owing to warmup, line-voltage variations, etc.)

(Audio magazine, May 1970; Herman Burstein)

= = = =