TAPE GUIDE (Dec. 1986)

Copying Phono Discs

Q. I own a rather extensive collection of 78-rpm and LP records and want to transfer many of them onto cassette tapes. In past years I have read several articles on how to clean up these old jewels, but alas, I did not save them. I own high-quality audio equipment with which to make the transfers, but I am at a loss as to how to proceed. I will appreciate your suggestions.

- Clifton T. Chadwick, Wheat Ridge, Colo.

A. One of the articles to which you refer is probably that by Peter Milton, "Get the Most Sound from 78s," in the June 1982 issue of Audio.

A great deal of help can be obtained with the aid of an equalizer and/or tone controls between the phono playback system and the cassette deck input; this is particularly the case for 78s.

Unfortunately, most preamps and integrated amps and receivers place the tone controls after the tape deck's out put, so they are not of help. Hence you probably have to rely on an equalizer, which can be very useful in achieving an optimum balance between extended treble response and minimum noise. A dynamic noise-reduction unit could be beneficial; perhaps it could be advantageously used with the equalizer. In setting such equipment, you must have confidence in your own ears rather than in settings arrived at by some formula.

Rise and Fall of EE Tape

Q. I thought that metal and Type II tapes were to be available for open-reel decks. What happened? Also, I am confused as to the difference be tween these and conventional open-reel tapes.

-Donald Bisbee, Columbus, Ohio

A. Still available from a few manufacturers, Extra-Efficiency or EE open-reel tape is made with particles similar to or the same as those used in Type II cassettes. The tape deck, for its part, must supply a higher bias and different treble equalization to get the most from this hotter tape. These electromagnetic changes are much like those required in a cassette deck in the switch from Type I to Type II tapes.

It turned out, apparently, that at speeds over VA ips, EE tape didn't present quite so obvious an audible advantage over ferric oxide as it had at the standard cassette speed of 11/4 ips. And then there was the problem of compatibility between the older non-EE decks and these new tapes, as well as the increasingly excellent performance found in the current cassette decks. For these and possibly for other reasons, the move toward EE tape has apparently come nearly to a halt.

More on Print–Through

Q. Does metal tape offer more protection against print-through than do the other types of tape?

-Robert R. Maigatter, Kewaunee, Wisc.

A. I do not know from experience, but on theoretical grounds, I would expect metal tape to be less subject to print-through because of its much higher coercivity, which makes it more difficult to magnetize. (Print-through results from one layer of tape on the reel magnetizing the adjacent layer.) If you are in the mood to experiment, you could investigate on your own, comparing metal tape with another type. Most of the print-through develops within the first two or three days after recording, so you don't have to wait very long for results.

Record Transfers to Tape

Q. I am in the process of transfer ring old 78-rpm records to tape. My collection includes old acoustics and post-1925 electricals, including a number of foreign make. My aim is to repro duce these records as they were in tended to be heard. I have improved their sound with an inexpensive, no-frills equalizer, but in setting this de vice I need information about the old equalization curves. I also need accurate information on the current phono standard, the RIAA curve.

-George Wheeler, Sea Cliff, N.Y.

A. Old 78-rpm records were recorded with a very substantial variety of equalization characteristics, depending on label and age, and I'm not in a position to provide such a listing in this column. All that can be said here is that some of these old records require more bass boost and some less; the same is true for treble cut (some were even recorded flat in the treble range).

The best course is to use what sounds best to you, taking into account not only frequency response but also noise. In other words, at times you may want to accept poorer treble response in exchange for reduced noise. Of course, this will require individual experimentation with each record, using your equalizer.

The RIAA playback curve calls for bass boost commencing (up 3 dB) at 500 Hz and leveling off (3 dB below maximum) at 50 Hz; total boost is 20 dB. It calls for treble cut beginning (3 dB down) at 2,122 Hz and continuing thereafter at a rate approaching 6 dB per octave; thus, for example, response is 13.7 dB down at 10 kHz relative to 1 kHz.

Onkyo has a preamp, the P-3030, with a single "78" equalization setting which may or may not match your 78s precisely, but which should come closer than the standard RIAA. Another de vice, the Esoteric Sound Re-Equalizer (reviewed in Audio, November 1985), can be used to obtain a more precise equalization match to nearly any 78-rpm disc.

What's a "Live Source"?

Q. I have read recommendations about which types of cassette tape to use when recording a "live source." Does this refer to recording a live source directly, or does it mean re cording a live source broadcast over an FM station?-Name withheld A. Recording a live source signifies that one is making a recording at the performance site itself-that there is nothing between the tape deck and the source except a microphone (and per haps a mixer).

For live recording on cassette, it is desirable to use metal tape to encompass the entire dynamic range, which can be as much as 70 dB or so. This will tend to minimize distortion and loss of high frequencies. But when FM stations broadcast "live," they use compression to reduce the dynamic range to about 60 dB or less. In that case, one can usually get good results by using a high-quality tape other than metal, such as ferric oxide, chrome, ferricobalt, or ferrichrome.

How Best to Dub

Q. I want to copy a cassette recording of songs I have written. I want the quality to be very good but the cost within reason. My choices are: A real time dub from my deck to a friend's deck; a high-speed dub on a $5,000 professional machine, which will cost $2; a real-time dub on a studio-quality cassette deck, which will cost $15.

Which would you choose?

-Steve Holliday, Santa Cruz, Cal.

A. I vote for the first course, namely a real-time dub with the aid of your friend's deck, assuming that your deck and your friend's are both of good quality and in good shape. Try dubbing from your deck to your friend's, and vice versa, to see which gives better results. If the original tape has NR, have both decks' NR circuits switched on (see "Deck-to-Deck Matching and NR: Straightening the Mirror" in the August 1986 issue).

Why not try things in the order you listed? First dub with the help of your friend's deck. If the copy does not compare favorably with the original, try a high-speed dub on the professional deck. If still not satisfied, then try the real-time dub on studio equipment.

Keep in mind that you cannot improve on the quality of the original, so the $15 course may sound scarcely, if at all, better than the free one.

Flat Spots

Q. My car's cassette deck does not automatically eject a tape when the engine is turned off, and tapes there fore are forgotten at times and remain in play position. Can this damage any of the deck's parts and cause a deterioration in playback response?

-Samuel J. Neiditch, Redlands, Cal.

A. The possibility of damage depends on what your deck does when the power to it is shut off. If the deck just stops, with the tape still squeezed between the rubber pressure roller and the capstan, the roller may develop a "flat spot" at the point where it contacts the tape and capstan. If the mechanism contains rubber drive wheels, they may develop flat spots too. Such flat spots cause wow and flutter, sometimes severe. While they are not necessarily permanent (the rubber tends to have a "memory" and therefore may recover its roundness), flat spots may become permanent if the deck is left in play position long enough. It is difficult for me to define "long enough," however.

On the other hand, some car decks go into "standby" when the power goes off, leaving the cassette in playing position but removing the pressure roller a short distance from the tape and capstan. This prevents flat spots.

It is possible, in hot weather, that a cassette left in either type of deck might warp enough to become unplayable or even enough to get stuck in the transport. Should this happen, the deck would have to be disassembled by a service technician in order to remove the tape.

Bright Sound

Q. My cassette tapes have a brighter sound when the equalization switch is in the 120-µS position. Why?

-Robert W. Thompson, Glen dale Heights, Ill.

A. I do not know whether you are referring to recording or playback or both. And I do not know if the EQ and bias switching are combined into one; I will assume they are. When the switch is in the 120-RS position, this ordinarily applies less bias than in the 70-RS position, resulting in increased treble response but also greater recorded distortion if you use tape formulations other than ferric. In playback, the 120 RS setting applies less bass boost which comes out to the same thing as less treble cut-and therefore yields brighter treble response.

Combining NR Systems

Q. Can the DNR (Dynamic Noise Reduction) system be used in conjunction with Dolby C NR? Will it enable me to retain the wide frequency response (20 Hz to 17 kHz) I now have with my tape deck? Can the DNR system be used for both playback and recording?

-Eric Gagne, South Hadley, Mass.

A. DNR is used solely for playback. Its purpose is to maintain the frequency response of the program source so far as the human ear can detect. It seeks to suppress high-frequency response, and thereby noise, only when the high-frequency content of the pro gram material is minimal; that is, it ought to operate only when the high frequency content is virtually masked by the noise.

DNR seeks to suppress noise al ready present in the program material (phono records, recorded tapes, etc.).

In contrast, systems such as Dolby and dbx NR cannot suppress noise in the program source; they suppress noise-and remarkably so-in the tape recording and playback system. The Dolby and dbx systems work by en coding (compressing) the signal being recorded and decoding (expanding) the signal that is played back; the downward expansion in playback also takes down the noise present in the tape system.

You could use a DNR system to reduce noise of the program source before the signal is fed to the tape deck.

Or you could use DNR after the playback signal has been delivered by the tape deck.

(Editor's Note: In my experience, DNR systems whose thresholds are not adjustable, such as those built into many car-stereo systems, do reduce high-frequency response, but only slightly. However, DNR systems with adjustable thresholds, such as those in some stand-alone noise-reducers, can usually be adjusted so as to eliminate most high-frequency noise with little or no discernible effect on treble response. Keep in mind, though, that it is rarely, if ever, possible to eliminate all audible noise without a slightly diminished treble. –I.B.)

(Source: Audio magazine, Dec. 1986, HERMAN BURSTEIN)

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