TAPE GUIDE (Sept. 1991)

Speed Mismatch

Q. I have a top-of-the-line dubbing deck and have noticed one problem with it, although I am not sure if it is of audible importance. One of the deck's transports takes 13 to 15 S less than the other to play a 45-minute cassette side. Is this something that can be fixed? Need it be fixed? An error of, say, 14 S in 2,700 S (45 minutes) is about 0.5%. I do not know if this really means something.

-John F. Page; Monterey Park, Cal.

A. Some decks have internal speed adjustments; I do not know whether yours is one of these. However, the speed deviation is quite minor, resulting in a pitch deviation that is probably inaudible to the overwhelming majority of listeners. Most people can detect a pitch deviation of a semitone-the difference between C and C sharp, for example, which is a deviation of nearly 6%. Many would have difficulty detecting a deviation of a quarter-tone, or about 3%. An eighth-tone difference is 1.45%, and a 16th-tone difference is 0.7%; very few people can detect them. Your deviation is still less, only about 0.5%, and those who can detect it are extremely rare. Only if you have absolute pitch might you consider doing something about your deck's mismatch between the speeds of the two transports. Matters are probably best left alone.

Recording FM on a VCR

Q. Supposedly I can make copies of simulcast programs by recording onto videotape the video signal from TV along with audio from an FM tuner. I am concerned about the problem with the 19-kHz carrier frequency for FM stereo since I am not aware of any VCR with an MPX filter. Is there any way to record FM stereo onto a videocassette?

-Romel Ramsey, Oxford, Ga.

A. Conventional VCRs (those not called Hi-Fi; do not be misled by the appellation HQ) ordinarily only accommodate mono sound; very few provide for stereo. Conventional VCRs perform linear recording along the edge of the videotape. The 19-kHz pilot signal of a stereo FM tuner could interfere with proper operation of the Dolby NR circuits in some conventional VCRs, and its harmonics could beat against the bias frequency to produce spurious sounds. However, modern FM tuners often incorporate MPX filters, preventing a problem. Look in your tuner's manual, or ask your dealer about it.

For the most successful recording of stereo, you are probably best off with a Hi-Fi VCR. The tuner's multiplex signal does not present a problem here. A Hi Fi VCR gives excellent audio results in terms of extended frequency response, high signal-to-noise ratio, low distortion, and accurate motion (low wow and flutter).

(Source: Audio magazine, Sept. 1991, HERMAN BURSTEIN)

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