TAPE GUIDE (Sept. 1988)

Taping CDs (Again)

Q. I understand that you cannot re cord a CD from the digital output of a CD player directly into the digital input of a DAT deck. Could you connect the CD player to an amplifier and then to the DAT deck for recording, or would the DAT deck still pick up the copy-inhibit flag to prevent the deck from recording?

-Matt Bacon, Humboldt, Neb.

A. There is no legitimate way to circumvent the copy-inhibit flag of a Compact Disc for direct digital copying. Furthermore, digital copying is inhibited by the different sampling rates for CD and DAT (44.1 and 48 kHz, respectively). But these factors do not prevent DAT copying from the analog output of a CD player. Moreover, assuming high-quality equipment, a DAT recording made from a CD player's analog output is usually of such high quality that it is barely (if at all) distinguishable from the Compact Disc.

Recording via an amplifier would not change the situation. There would be no inhibition against recording signals via analog connections between the amplifier and the DAT recorder. If digital connections were used from amp to recorder (which some new amps al low), all flag bits would presumably be passed on with the rest of the signal. In any case, the incompatibility between the sampling rates would still prevent recording.

Hum

Q. Lately, my audio system has been producing an extremely obtrusive hum. I have traced it to the right output jack of my cassette deck. Any advice?

-Mark A. Ortega; Albuquerque, N.M.

A. The cable between the jack and the rest of the system may be defective or not securely connected at one end or the other. Detach the cable, and then reinsert it tightly with a twisting motion. If this doesn't help, try a different cable. If you don't have an extra cable, temporarily borrow the left one.

A good cleaner, such as Cramolin, will help here too. Another possibility is that the right output jack is not properly grounded. There could be a cold-solder joint which looks okay to the eye but isn't. To check this, you'll have to go inside the deck. The cold-solder joint could be either at the ground side of the jack or where a lead from the jack goes to ground. Unless you have the necessary technical know-how, you should leave the task to an audio technician.

The hum could also be originating somewhere in the playback electronics--including in the power supply for the right channel--or it could be due to a poor connection between the play back head and the playback electronics. It might be that you're hearing r.f.i. or e.m.i. radiation from some piece of gear to this right output jack of the cassette deck. I would suspect this if you suddenly started hearing the hum after moving the equipment around.

This isn't the most likely of sources, however.

Hi-Fi VCR Use

Q. I have a hi-fi VCR and have used it to record audio from CD and other sources. Do I need a PCM processor with the VCR to make live recordings?

-Charles Scott, Wichita, Kans.

A. When set in the hi-fi mode, a hi-fi VCR employs FM modulation of the audio signal to make a recording. When either a hi-fi or conventional VCR is used with a PCM unit, it makes digital recordings.

Hi-fi VCRs produce excellent frequency response, high signal-to-noise ratio, low distortion, accurate and stable speed, etc. The results are quite comparable to those obtained when using a PCM processor with a VCR. While a VCR-PCM combination may be measurably (though slightly) superior to a hi-fi VCR, it is not likely to be audibly superior.

In sum, I feel there probably is no advantage to recording with a PCM processor.

Low-Price Decks and High-Price Tapes

Q. I presently own a dual cassette deck costing under $200. It has worked great with Type I and II tapes for over a year. Because of metal tape's high cost, I never used it until last week. After recording on it, I noticed excessive distortion in playback.

Since my deck does not have a front-panel bias selector, I have to assume that the automatic sensing mechanism for tape type is working properly and providing proper bias. Following the deck manufacturer's instructions for metal tape, I let the deck's meters peak at +5 dB. The distortion, while most noticeable in the low bass, is also audible in the upper midrange. It sounds to me like intermodulation distortion: When a low bass note occurs, the upper midrange and the high end break up.

I noticed that another tape manufacturer, Memorex, does not make metal tape, giving this reason: "We feel that most cassette decks are not properly matched to these tapes because of circuit or head design, delivering insufficient bias and causing distortion." Could this be true, or am I overlooking something?

-Keith Richardson, Mason City, Iowa

A. Metal tape, as contrasted with the other types, requires much more bias; it could well be that your deck doesn't supply enough for the brand you bought, or perhaps for any brand.

If treble is accentuated, this confirms that bias current is insufficient. Metal tape also requires considerably more audio signal current to the record head, and your deck may be inadequate in this respect. In other words, the higher level of required signal cur rent may be overloading the record electronics.

Further, the record head must be of superior construction to drive the required amount of bias current through it. When metal tape first appeared, existing record heads could not handle that much current. Therefore, compromises were made in the manufacture of metal tape, reducing its coercivity below that which was feasible, and thereby reducing its ability to achieve superior treble response. Even today, such compromises may be in effect. It is likely that a relatively low-priced deck such as yours has an inadequate record head for use with metal tape.

All in all, it seems that Memorex's statement applies to your deck. Fortunately, you can still do very well with Type I and Type II tapes.

(Source: Audio magazine, Sept. 1988, HERMAN BURSTEIN)

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