TAPE GUIDE (Apr. 1984)

What Can $300 Buy?

Q. When recording at 0 dB on a cassette deck's meters, what sort of frequency response is necessary at this level in order to faithfully reproduce a top-quality LP? Can such a cassette deck be found in the $300 price range?

-Jim Kincannon, Hammond, La.

A. Top-quality LPs achieve response out to about 15 kHz. However, for most music, particularly classical, the treble frequencies tend to be at substantially lower level than the mid range frequencies (and than much of the bass). Therefore, despite the treble boost applied in recording, one can record a tape at or close to the 0-dB level without substantially impairing response in the high treble.

However, there are some qualifications. As indicated above, some kinds of music have higher relative treble levels than do other kinds-rock music, for example. If one is using Dolby B instead of Dolby C, there is more chance of saturating the tape and losing highs; with dbx there tends to be still less chance of tape saturation.

Then there is the question of what 0-dB level signifies. In some decks it corresponds to Dolby level, while in others it is about 25%--about 2 dB--higher. If 0 dB corresponds to Dolby reference level (200 nanowebers per meter), there is less chance of tape saturation when recording at a level that doesn't exceed 0 dB.

All in all, if frequency response at 10 kHz does not drop more than about 3 dB relative to 1 kHz when recording at 0-dB level, and if one is recording material without unusually strong highs, essentially faithful response out to 15 kHz can be achieved. There are a number of cassette decks today in the $300 price range that can do this, and thereby faithfully reproduce a high-quality LP record.

Dolby Level

Q. What is Dolby level, and what is it supposed to be used for?

-Jeff Pagels, Largo, Fla.

A. Dolby level is a recording level which, at 400 Hz, produces a signal level of 200 nanowebers per meter (200 nWb/m) on the tape. When using Dolby noise reduction, there has to be a correspondence (within 2 dB) between the recording and playback levels going through the Dolby circuitry: this is referred to as proper tracking. In playback, the meter or other indicator shows Dolby level at a specific point, assuming the indicator has been properly adjusted. In recording, level is adjusted (sometimes by the user, if the deck so provides; otherwise, by the manufacturer) so that a 400-Hz tone reads at Dolby level in playback. If there is mistracking--poor correspondence between recording and play back levels going through the Dolby circuitry--high-frequency response tends to suffer. This occurs because the amount of treble boost supplied in recording isn't matched by the same amount of treble cut in playback.

Channel Dropout

Q. I would appreciate your advice on the following problem with my open-reel tape deck. Recently I noticed that a taped FM broadcast would have a dropout of one channel for a period of time. I phoned the station and was told that the problem was theirs, not mine. I experienced a similar problem with another station, and it, too, assumed the blame. I would be reassured, except that I seem to experience the same problem in taping phono discs.

-Mrs. H. E. Hlad, Bayonne, N.J.

A. If you have the one-channel dropout problem with both phono and FM recordings, but never when listening directly to FM or phono, the problem would most likely lie in your tape deck. You will have to refer it to an authorized service shop. There is a very slight possibility that the tape itself is at fault, owing to excessive oxide shedding. If you re-record on the tape and the dropout shows up in the same region, the tape would be indicated as the culprit. You might also try recording on virgin tape to see if the problem then disappears.

If the problem occurs when listening directly to a sound source, preferably phono, then the fault lies somewhere in your system other than the tape deck.

And, as before, you would need the help of a service shop.

(Audio magazine, Apr. 1984, HERMAN BURSTEIN)

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