Tape Guide (Sept. 1981)

Brush Strokes

Q. I am generally pleased with my cassette deck, except for one characteristic. Record warp so minor as to be un noticed when playing a disc is "amplified" during the recording process to the extent that distortion makes the tape un playable. I have tried various kinds of tape with no success. In order to get a good tape recording of a disc, the disc must be in nearly mint condition. How can I solve the problem?

- John Holtzhauer, Dumfries, Va.

A. Your problem is not an uncommon one. It seems characteristic of some cassette decks that they are rather easily overloaded by a low-frequency signal of high magnitude. One possible solution that is quick and cheap is to attach a record brush to the cartridge shell. This might damp the warp signal, but of course you would have to increase the tracking force to compensate for the resistance of the brush. A similar but more expensive solution is to buy a phono cartridge with a built-in brush, such as the Shure V15 Type IV, which has a recognized ability to deal with record warp. Still another and possibly better solution is to interpose a subsonic filter between the tape output jack of your system and the tape deck. An example is the Ace Model 4000.

Poly-Saturation

Q. Is the danger of saturation one of saturating the magnetic material of the record head itself by boosting the highs with the equalization circuit?

- D. Ohde, Weaverville, Cal.

A. In speaking of the danger of saturation in tape recording, the reference is usually to the magnetic coating of the tape. The problem arises chiefly in the treble range. Treble frequencies receive a good deal of boost in recording, particularly at the slower speeds, in order to overcome several kinds of losses. Up to a point, the amount of signal recorded on the tape is proportional to the amount of signal presented by the record head. But beyond this point, the tape tends to saturate so that the amount of signal recorded on the tape does not increase; in fact, the recorded signal level may even decrease.

A head of poor construction and/or poor materials may also saturate, although this is more likely at the low frequencies. On occasion, saturation may occur in the electronics owing to poor design. In sum, saturation can occur on the tape, in the heads, or in the electronics; most often it is on the tape.

Which Switch?

Q. I use CrO2 tapes and notice that music sounds better when I set the tape selector switch of my deck to the "standard" position. I would like to know why. Also, is it harmful to the deck if I have the selector switch on "standard" when using CrO2, tapes?

-Scott Eldridge, Crailsheim, Germany

A. In the "chrome" position, the deck supplies more bass boost in playback than in the "standard" position. Accordingly, treble frequencies are depressed more (relative to, say, 1 kHz) in the "chrome" position. In the "standard" position, treble is depressed less, and the sound is brighter--which you apparently find pleasing. No harm is done.

A Definite Zero

Q. How do you define 0 VU recording level?

- Jerry Pulice, Staten Island, N.Y.

A. The definition depends on whether you are using a peak reading device, such as a fluorescent bar or peak reading meter, or whether you are using an average reading device such as a true VU meter.

In the case of the VU meter, 0 VU corresponds approximately to the re cording level which produces about 1 percent harmonic distortion on the tape at a frequency in the range of 333 to 1,000 Hz. Depending on the tape used, distortion may be slightly above or below the 1-percent figure.

In the case of a peak reading device, 0 VU corresponds to approximately 3 percent harmonic distortion, which is generally considered the maximum compatible with high quality results. The difference between 1 and 3 percent distortion corresponds to about 6 to 8 dB difference in recording level. An average reading device, such as the VU meter, needs at least this much margin to compensate for the tendency of the meter to lag behind transients.

(Adapted from: Audio magazine, Sept. 1981; Herman Burstein )

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