Tape Guide (Feb. 1979)

Tape Bias

Q. What is optimum tape bias?

-Frederick Vasquez, Regina, Sask., Canada.

A. Optimum bias is that which, together with optimum equalization and drive level (amount of signal fed to the record head at 0 VU reading), results in the most satisfactory combination of low distortion, extended treble response, and high signal-to-noise ratio. Optimum conditions vary with the tape speed and the type of tape.

Particularly at the slower speeds, one cannot merely set the bias for minimum distortion as this would, usually, result in excessive bias erase (inadequate treble). One could compensate for such treble loss by increasing the treble boost, but this increases the chance of tape saturation at high frequencies. Therefore, compromises are in order: One compromise is to re duce the bias somewhat, without an increase in distortion. Another compromise is to increase treble boost somewhat, without an excessive risk of tape saturation. Still another compromise is to reduce the drive signal somewhat, which results in less distortion and less risk of tape saturation, yet without excessive reduction in the signal-to-noise ratio.

Accordingly, the manufacturer of a tape deck must, for a given tape and a given speed, juggle the three factors of bias, equalization, and drive level to arrive at what he considers to be optimum performance in respect to distortion, extended treble response, and noise.

Two-Part Taping

Q. I play piano and would like to record the bass part of a song on Track A, then go back to the beginning and fill in the rest of the song on Track B. How can this be done?

- Bruce LaRocca, Chelsea, Mass.

A. The solution to your problem is in the use of a tape deck which permits synchronized sound-with-sound re cording (known by various trade names such as Sel-Sync, Simul-Sync, etc.). With such a tape deck there is a switching system that temporarily allows the upper section of the tape record head to be used as a playback head. Thus, the left (upper) channel of the record head plays Track A at the same time that the right (lower) channel records Track B. Since both channels are in the same head, one thus obtains exact synchronization.

Taping Mike

Q. I need advice in choosing a microphone for recording live instrumental music, anything from a flute duet to a 60-piece concert band. Should it be omnidirectional or cardioid? Should it be dynamic or condenser? I am willing to spend up to $200.00.

-Joseph Corvo, Woodland, Cal.

A. You might be happy with a top quality dynamic microphone, with an omnidirectional pattern. An omni directional mike tends to give a wider and flatter response than a cardioid.

On the other hand, $200 can buy quite a good condenser mike. Your best course of action is to go to a dealer and listen to several mikes by recording your voice or a solo instrument on tape. Perhaps, you can even find a dealer who is willing to let you try out two or three different mikes at a recording site.

One other way to go is to buy a mike with interchangeable capsules, which will give you different directional characteristics, though the operating principle will, of course, remain the same.

Tape Longevity

Q. If I play a cassette 150 to 200 times, will the cassette hold up better than a phonograph record?

- Steve Leder; Mt. Vernon, N.Y.

A. On the whole, I believe the answer is yes. Initially, there might be a slight loss in the highest frequencies during the first few plays--perhaps as much as 2 to 5 dB in the range of 10 to 15 kHz--but after that you should be able to get many hundreds of plays without noticeable change. The initial loss to which I refer will vary with the type and brand of cassette tape used.

(Source: Audio magazine, Feb. 1979; Herman Burstein )

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