TIME FOR A CHANGER

Return of the Changer?

Multiple-play turntables-record changers, if you prefer-have apparently disappeared from all but the cheapest systems. They had their sonic drawbacks, but they were certainly a convenience.

And they may be coming back--though not for phonograph records.

At one time, Benjamin imported a 10-cassette changer from Lenco. Now Sony (who once had a changer for open-reel tapes!) is introducing a new model, the MTL-10 Cassette Bank, also holding 10 cassettes.

Compact Disc changers are also likely to arrive in a few years. Philips is admittedly looking into changer design, and they're not alone. The mechanism will have to be completely different from a phono changer's, as it may be impractical to put the laser assembly on an arm that can swing in between the top and bottom disc stacks during play, and swing out again to let the next one drop. (You'd have to play the CDs label-side down, then, too). More likely, it will work something like the old Thorens multiple-play model, shifting records one at a time from a stack to the platter and on to a second stack.

It will also eliminate the record producer's old dilemma of how to sequence the sides of a multiple-disc album. Sequenced for manual play, each disc would bear two consecutive sides (1-2, 3-4, 5-6, etc.); in changer sequence, the sides would be arranged for easy stacking (1-6, 2-5, 3-4). Since CDs only have one side, no problem.

How long will we have to wait? Perhaps not very. Two days after penning these speculations, I learned that Aiwa, Hitachi and Marantz showed prototype CD changers at the Japan Audio Fair last October. The Marantz model held 10 discs, Hitachi's held 31, and the Aiwa held 99 discs; let's hope the latter two, at least, have random-access changing, so that one could play only selected discs without having to remove and reshuffle them. They probably do: Denon's 100-disc prototype, also shown in Tokyo, can be programmed to play any 15 selections in its store, no matter which discs or tracks they're on.

Don't look for the Aiwa or Denon to show up in many homes; they're presumably for commercial use of various types. Ten-disc models like the Marantz are certain to show up as home equipment, and something the Hitachi's size just might as well, though it will also probably sell better in commercial/institutional markets.

Space-Age Microphones?

High Technology ran a piece a while back (July/August 1982) on the use of optical fibers as sensing devices-including their use as acoustic sensors.

Microphones? Phono cartridges?

Well, probably not, at least not in the near future. The techniques described in the article involved long lengths of fiber to produce only subtly measurable effects, such as optical phase interference. And the effects produced, all purely optical, must be converted to electrical signals before use in a sound system. Possibly the fibers could be used to modulate a laser beam, but that would work only for analog recording; so far, all the laser sound recording I've seen has been digital. If an Audio reader can prove me wrong, and come up with a good fiber-optic microphone or cartridge, I'd like to see and hear the result. The same holds true for the use of fiber optics as magnetic sensors: Tape heads, anyone? Years ago, I think in Analog, I read of another interesting space-age microphone design: A thin, mildly radioactive rod at the center of a cylinder lined with radiation-sensing material. As sound waves changed the air's pressure (and hence density) in the space between the radiation source and sensor, the sensor's output would change, yielding an electrical signal. Seems to me the idea would work if the cylinder were small enough and the sensor fast enough. But I bet the output signal would be awfully noisy. Radiation hazards would have to be considered, too, though I doubt they'd be any worse than a smoke detector's. Any readers know more?

Digital Peace Parley

The digital revolution has generated as much heat as laser light. At one pole stand those who feel that digital is the best thing yet to happen to sound; at the other stand those who feel that it's the worst. And in between are those who feel that digital has a distance still to go-to reach perfection, say some; to reach acceptability, say others.

And so SPARS (the Society of Professional Audio Recording Studios) will hold a conference from Thursday, March 8 to Saturday, March 10, called "The Digital Revolution: In Search of a Peace Treaty." It will feature eight seminars, including one by Audio's Len Feldman ("CD or Not CD, Was That the Question?"), a concert ("Ear Training"), and a debate (in the form of a mock trial) between Doug Sax and John Eargle. Participants are also invited to prepare their own position papers for distribution to others at the conference.

Registration is $325, with discounts for early registration, SPARS membership, and student observer status. For information, write to' SPARS, P.O. Box 11333, Beverly Hills, Cal. 90213, or phone: Gary Helmers (213/651-4944, California), Dave Teig (212/355-1008, New York) or John Woram (516/764-8900, New York).

Music Hath Charms

"Superstitious" folk beliefs have often been precursors of real scientific breakthroughs. Which is why W. Wilson Mayne, writing in the English scientific weekly New Scientist last summer, was perplexed.

He'd heard, in his travels through the Orient, that ground-up phonograph records are an antidote for snakebite.

That struck him as nonsense at first, but when he heard the same thing in another country, thousands of miles away, he began to wonder if there might be something in it.

Turns out there was, according to a later letter from a reader in Sweden: "The old records are made of Bakelite, a phenol/formaldehyde resin which releases small amounts of formaldehyde ... when pulverized.

"Formaldehyde is known to deactivate proteins and peptides, and the snake venoms contain active components of peptidic character. .. "It would probably be quite easy to develop an efficient antidote against snakebite using a substance that releases formaldehyde in a controlled way....,, So there you are only weren't the old records made from shellac rather than Bakelite? So I suspect the mystery is still unsolved-or it is really a superstition after all? Today's LPs won't work, in any case. CDs either.

K vs. "k"

As long as there has been an Audio (and longer), the quantity 1,000 has been abbreviated by a lowercase "k," as in "15k resistor" (sometimes spelled out as "15-kilohm resistor"). That's still true, but sharp-eyed readers will have begun to spot occasional instances of capital "K" when digital matters are discussed.

The capital "K" stands for 1,024--two to the tenth power, sometimes called a "binary thousand." Digital matters, being based on two-valued logic (yes/no, on/off ...), work out more naturally to powers of 2 than powers of 10, and 210 comes up often enough to be called after its decimal cousin, 103.

This, by the way, is why the same computer memory may be referred to as either "64K" or "65K"-64K is 65,536. Perhaps it would be more logical to equate 64K with 65k, but who said computer people were logical?

Prerecorded Progress

Prerecorded cassettes have traditionally sounded pretty bad, with more limitations on high-frequency response than on noise, and distortion creeping in more often than on disc releases. You paid more for the recording, but had less to show for it. The tape used was often the cheapest possible, and the flimsy cassette shells tended to jam--especially the ones whose tape viewing windows had no transparent covers to keep out the dust. On the other hand, as long as everyone was listening through limited-fidelity portables, it didn't matter much.

While such portables still exist, more and more listeners have cassette systems of reasonably high fidelity-at home, in their cars, or in their pockets-and the record industry is finally starting to catch on: BASF has been pushing their premium ferric and chrome tapes to duplicators, and some labels (such as A&M and Sine Qua Non) are beginning to use the latter. However, neither label's chrome cassettes have the Type II recognition notch, so decks with only automatic playback equalization setting will play them with the wrong (120-uS) EQ. Last year, Electro Sound introduced cassette duplicating equipment which used the Dolby HX Professional system; this year, Warner (including Elektra/Asylum, Atlantic, and presumably Nonesuch) announced that they'll use HX Pro for all their prerecorded cassettes. Capitol (which makes tapes for other labels as well) and other duplicators are reportedly on the verge.

The HX Pro system (developed by Bang & Olufsen as an improvement on Dolby's original HX system) increases tape headroom in recording. It does so by adjusting bias instantaneously, cutting it when the signal is rich in high frequencies (which have a biasing effect), to avoid saturation due to over-biasing, then restoring it to normal when the treble content goes down again. Both B & O and Harman/Kardon home decks have the system.

In October, WNCN, a New York classical FM station, began a 13 week series of programs produced entirely from cassettes. The Sine Qua Non Seven Star Series was, naturally, sponsored by Sine Qua Non, which produces and distributes cassettes from the Varese Sarabande, Orion, Northeastern and Crystal Clear labels.

Since mid-1981, In Sync Laboratories, of New York, has been offering its tapes in Dolby C as well as Dolby B formats, both duplicated in real-time (rather than at high speed) on Nakamichi 582 decks, using TDK SA-X tape. The tapes are sold in stores, and also by mail from the company, at 2211 Broadway, New York, N.Y. 10024. The catalog offers 108 titles, 99 of which are available in both formats-the other nine were dubbed from 78-rpm discs, so the extra few dB of noise reduction won't matter much. Dolby C tapes are also available from Delos and Direct-to Tape Labs, and, on special order, from Mobile Fidelity.

The dbx tape catalog now contains 56 titles, from 20 record labels, at $14.95 apiece. As the number of dbx-equipped home and car decks rises, and with the availability of dbx decoders for Walkman-type personal tape players, that number should rise. At least one other source (Direct-to-Tape Labs, again) offers dbx-compatible tapes, and I wouldn't be surprised to see more sources emerge.

Not all the tape news involves compact cassettes. Mobile Fidelity now has PCM digital cassettes (Beta or VHS format). And Sonic Arts, of San Francisco, is offering its recordings on 15-ips, half-track tapes (two 10 1/2-inch metal reels for $198)as well as on PCM digital cassettes for $75 apiece. The Sonic Arts tapes are not actually sold, but leased, subject to licensing agreements which forbid the user to make reproductions in any form. Digital copies of the PCM tapes will be traceable, as the cassettes have digitally encoded serial numbers. On the other hand, each 15-ips tape comes with a copy of the LP made from the same master tape, so one can check one's turntable and cartridge against the tape.

Digital Diagnostics

In my front hall is a neat pile of comatose audio equipment, ready for its run to the repair shop. I'm handy enough with a soldering iron to fix whatever's wrong, but I lack much of the knowledge and all of the time to diagnose just what needs fixing.

Come digital, this may no longer be a problem. It's not that digital circuits will be easier to fix, at least by those of us brought up on analog. But it is possible, and probably not too expensive, to build self-diagnostic facilities into almost anything which already has a microprocessor (which includes a good many analog components now), and probably even easier to build them into components which are digital almost all the way through.

There's a precedent: Larry Schotz's Micro/CPU-100 tuner, first sold by Sherwood and also later by Draco Labs, could be fitted with a diagnostics board which found bad circuits or components and named them on the station display. The board was plugged in at the dealer's, but as digital prices come down, similar functions might be built in.

I can hardly wait. Preamps will still be a nuisance to fix (all those cables to unplug and keep straight), but it will save lugging heavy power amps across town to the shop.

Styli Saved by Dr. Scholl

With my last tonearm, I lost a few styli by accidentally letting the arm fall to the metal surface of my turntable base. My new arm doesn't let that happen, but before I got it, I found a solution at my neighborhood drugstore: Moleskin, from the foot care department. Cut a piece to cover the area where the stylus might fall, dye it the color of your choice, then just peel off the backing and stick it onto the top of the turntable base. Sorry I can't show a picture of this. I took the moleskin off again when I got my new arm, which doesn't let the stylus fall that far.

(adapted from Audio magazine, Feb. 1984)

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