TAPE GUIDE (Nov. 1986)

Correct Recording Level

Q. My question deals with setting the right recording level to obtain the widest and flattest frequency response with my cassette deck, a Nakamichi BX-300. The instruction manual and Audio's review of the deck indicate that response of 20 Hz to 20 kHz is achieved at a -20 dB recording level.

Is that the level at which I should record? If so, won't this result in a poor signal-to-noise ratio?

I took a crash course in recording engineering a couple of years ago, and the instructor told us, "Record as high as possible without distortion" so as to achieve a high S/N ratio. I have been following this advice. However, I don't know if I'm getting flat response from 20 Hz to 20 kHz, because Nakamichi's manual for another model says, "The cassette recorder's response depends upon recording level. The louder the program becomes, the more likely it is that high frequencies lose clarity and brilliance."

So it seems that -20 dB is the preferred recording level. Should -20 dB be the lowest the meter reads? The average? Or the highest?

-Ariston B. Malolos, New York, N.Y.

A. The industry has settled on-20 dB as the recording level for testing a deck's frequency response. If you are interested in recording test tones and maintaining flat response throughout the audio spectrum, record at the-20 dB level. However, if you are interested in recording music and other program material, record (with your deck) at a level several dB above zero. The Nakamichi instruction manual states that re cording level should be such that program peaks read about +8 dB for metal-particle tape and about +5 dB for other tape types.

The reason you can record at a higher level with program material than with test tones is that normally such material has a substantial decline in energy as frequency rises. This decline pretty much offsets the tendency toward tape saturation with rising frequency, which is due largely to the treble boost applied in recording. Test tones, by contrast, are fed into the deck at a constant level throughout the audio range, and the treble boost applied to them saturates the tape unless recording level is reduced.

The level at which you can record program material without losing treble response depends on the nature of the material and on the type and brand of tape you are using. Hence, experimentation is advisable. Trust your ears. Try copying and comparing with a phono record or with FM interstation noise (the de-emphasis provided by the FM tuner reduces acoustic energy in the treble in a way comparable to the treble decline in program material). It may be wise to provide a safety margin of a few dB when taping live music or other material with a very wide dynamic range, as in the case of many CDs.

Wavy Tape

Q. I have been using a very high quality cassette tape brand for about seven years, and only recently did I have any question as to its performance and reliability. After playing a short segment of a not often-used cassette, I removed it from the deck and noticed that the top and bottom edges of the tape were quite wavy. This can spell disaster unless I can eliminate the cause of the waviness.

-Ora Troyer, Alburtis, Pa.

A. If the problem of tape deformation has occurred only with one cassette, the cassette is probably to blame, owing to faulty internal guides or other components. However, if waviness occurs in several cassettes, the tape deck is apparently at fault. Im proper tape tension, a faulty pinch roller, or other factors affecting a tape's progress could be responsible; excessively fast and insufficiently smooth winding speed might also cause tape deformation. The thinner the tape, the more easily is it deformed. For example, C-120 would be more easily de formed than C-60.

Cassette Deck or VCR?

Q. I want to make high-quality dubbings of cassettes. I was planning to buy a second cassette deck, but recently listened to a hi-fi VCR and was impressed. Perhaps I should buy this instead. What is the dynamic range capability of a good cassette deck? Can I expect better audio quality from a hi-fi VCR?

-Michael J. DeVoge; Conneaut Lake, Pa.

A. A cassette deck with Dolby C NR achieves a weighted S/N ratio upwards of 70 dB; one with dbx NR gets into the 80s and perhaps up to 90 dB or so. Hi-fi VCRs can also achieve S/N ratios in the 80s. I suggest you listen both to a high-quality cassette deck and to a hi fi VCR to ascertain whether there are significant differences to your ears.

Excessive Bias

Q. My cassette deck has a bias control, and with all the brands of tape I have tried, the best results are obtained with bias set at minimum. Even so, I sometimes find that there is a treble loss. Could you tell me what is wrong?

-Andy Warren, Miami, Fla.

A. There probably is a misadjustment inside your deck in the direction of excessive bias. A competent technician should be able to remedy this easily by adjusting the internal bias control, if there is one, or by using a resistor of proper value to reduce the bias suitably. If he makes the adjustment correctly, you should be able to obtain best results with most tapes when the external control is set about midway.

By any chance, do you have your deck set for the wrong tape type? If you are using Type I tapes but have the deck set for another type, bias will be excessive. Some decks provide for automatic bias-setting according to holes in the cassette shell. If your deck is of this type, it may be misfunctioning in this respect.

Which Deck for Dubbing?

Q. I have a good two-head deck and a better three-head deck. Which should I use for playback? Which for recording from existing tapes?

-Joseph P. Bumbas, West Mifflin, Pa.

A. In theory, the better deck should be used for playback in order to minimize noise, which is usually most intrusive in playback, and maximize high-frequency response. However, theory isn't always confirmed by practice, and so it is wise to experiment. First try the three-head deck for playback and the other for copying over a brief stretch of tape. Using the same side of the same cassette, reverse the roles of the two decks. Now you have two copies on the cassette. Play both and note whether you can hear a difference. If so, decide which version you like better and use the record/playback procedure which yields that result.

What's Wrong with C-120

Q. Why is there a general prejudice against C-120 tapes? Even the manufacturers seem ashamed of them. I have used Sony C-120s for over 12 years with fewer than 10 failures in hundreds of cassettes. For lectures, conferences and speeches they are invaluable. Sony has just discontinued all C-120s in Canada. They claim that C-120s do not sell well. Without any advertising, it's a wonder that they've been able to sell any at all in the past 15 years.

-Jeffrey Asher, Montreal, Que., Canada

A. The prejudice against the C-120 appears to stem from its greater tendency to foul up mechanically, develop print-through, and exhibit distortion compared with the shorter C-90, C-60, and C-46 tapes. You may have had better luck than average with respect to fouling, possibly because of the deck you are using. Further, the other problems would be less worrisome for speech than for music reproduction. In my own case, I found the C-120s not as clean-sounding as the others. How ever, with time everything in the tape field has improved, and it could be that today's C-120s are substantially improved over yesteryear's. It would be interesting to get other readers' reactions on the subject of C-120 performance.

Cassette History

Q. When was the cassette, developed by the Philips Co. of the Netherlands, first available to consumers? Could Philips have manufactured a four-channel cassette deck? Whatever happened to the Elcaset?

-Tony Perkins; Los Angeles, Cal.

A. The date I have for introduction of the cassette deck to consumers is 1963. Philips probably had the technology to produce a four-channel deck, but such was not the intention.

Stereo was then pretty much the thing-having been introduced in 1958-and has essentially remained so; four-channel never really got going and, except for a flicker here and there, has essentially died.

Rapid advances in cassette decks and tapes tended to make the 3 3/4-ips Elcaset superfluous, and the powers behind the cassette format were very strong. Further, there was an important lesson to be learned from the four-channel experience, where several systems were simultaneously on the market: If a new development is to succeed, it is vital that the audio industry join forces in presenting it in a single format. Look at the trouble AM stereo is having because of the several competing systems on the market. (Thank you for nothing, FCC!)

(Audio magazine, Nov. 1986, HERMAN BURSTEIN)

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