TAPE GUIDE (Jun. 1992)

Pleasant Playback Equalization

Q. My cassette deck is several years old and has three equalization settings: CrO2, "LH," and FeCr. When playing CrO2 tapes, the only ones I use, and switching to "LH," I notice that the highs are boosted and that my VU meters give a higher reading.

There seems to be more information on the tape than in the CrO2 position. Also, the recording sounds louder. Why? Is there less tape noise in the CrO2 position? (I don't worry about noise because I use an outboard dbx noise-reduction unit.)

-Gary Guarneri, Danville, Cal.

A. In the CrO2 playback position, the deck provides very substantial bass boost, starting (up 3 dB) at 2,274 Hz. In the "LH" position, it provides somewhat less bass boost, starting at 1,326 Hz. Looking at this conversely, treble is depressed more in the CrO2 position than in the "LH" one. Accordingly, when you play your tapes in the "LH" position, you get more treble than in the CrO2 position. Normally, for flat test response with CrO2 tape, you should use CrO2 playback equalization. But if the sound is more pleasing to you with "LH," there is no law that you should deny yourself.

The increased treble with "LH" accounts, at least in part, for the increase in loudness and the higher VU reading.

It may also be that the equalization circuits in your deck are such as to produce an overall increase in output in the "LH" position.

When using CrO2 playback equalization, you not only depress treble more, but you also reduce noise more.

However, if you find that noise is not a factor in your listening pleasure, you should simply use the playback equalization that sounds best to your ears. (However, in recording be sure to switch the tape selector to CrO2 when using CrO2 tape or equivalent, Type II tapes.)

Head Longevity

Q. Please compare the longevity, in hours, of audio cassette heads, VCR heads, DAT heads, etc.

-Ronald B. Freeman, Freehold, N.J.

A. I do not have sufficient information to answer your question specifically. Also, I doubt that specific answers are possible. In the case of heads for audio cassette decks, the materials of which the heads are made are chosen not only with respect to head life but also with respect to distortion and the ease of machining them to achieve fine, sharp gaps. Therefore, a manufacturer may elect to use heads with, say, a life of 10,000 use-hours instead of others having a life of 20,000 hours but with inferior characteristics with respect to distortion, etc.

Another factor in head life is tension of the tape against the heads. In most cassette decks, tape-to-head contact is achieved by a pressure pad within the cassette shell, whereas in others (such as Nakamichi decks), a finger is used to push the pressure pad away and the torque applied to the take-up and supply nubs keeps the tape properly snug against the heads. Eliminating the pad's pressure tends to in crease head life.

As a rough guess, well-made heads in a quality cassette deck operating at the standard speed of 1 7/8 ips tend to have a useful life of about 10,000 hours. However, the meaning of "useful" is open to question. If the gap of a playback or record/playback head widens so that response beyond, say, 13 kHz declines sharply, is this head no longer useful? For an adult whose hearing extends only to 12 kHz, this head may still be okay. It may also be okay for a teenager who suffers pro found hearing loss owing to excessive hours at loud rock sessions.

VCR heads tend to have appreciably shorter life than audio cassette heads because the relative speed between the tape and heads is much greater in the case of VCR. As a very rough guess: 1,000 to 2,000 hours at standard videotape speed. Life is extended by using the long-play (LP) and extra-long play (EP or SLP) speeds.

Like VCRs, DAT recorders also have their heads on rotating wheels, which increase tape-to-head speeds. So DAT heads might have roughly similar life-spans even though the tape speeds, tape-to-head speeds, and head de signs are different.

(adapted from Audio magazine, Jun. 1992, HERMAN BURSTEIN)

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