Behind The Scenes (Aug. 1978)

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As I have said many times before (I hope not ad nauseum), the audio industry is one of the most dynamic, fastest -growing segments of our scientific community. The fact that the Audio Engineering Society sponsors three conventions every year is a convincing indication of its vitality. Every year, each succeeding American convention becomes ever bigger and more comprehensive. So it was with the 60th AES convention, held in Los Angeles May 2-5th of this year. It has become almost a cliché to state that "attendance was up, more papers were presented, there were more exhibitors than at any previous convention." Needless to say, this "high-water mark" is sure to be topped by the New York convention in the fall ... and so it goes.

If the entrants in the "digital derby" got out of the starting gate at the 58th AES convention at the Waldorf, at this convention it was obvious they had reached the first turn and were jostling for position, but with the homestretch not yet in sight. There were nine papers presented on various aspects of digital recording, as well as demonstrations of digital recorders from Soundstream, JVC, 3M, Technics, Mitsubishi, and a non-official demonstration of the Sony PCM unit by that bearded savant of Cerwin-Vega, Gene Czerwinski.

Painfully aware of the debacle caused by non-compatibility and non standardization of quadraphonic sound, the AES has wisely set up a "Digital Audio Standards Committee." There have now been five meetings of this group, and while there seems to be general agreement that a 16-bit system is desirable for digital recorders, the matter of sampling rates seems to have created a stumbling block. On the one hand is a group who advocate a single standard sampling rate for digital recording whether the units employ fixed heads or rotary-scanning heads. On the other hand, there are proposals for a certain sampling rate to be used with consumer-type PCM units for rotary heads and another sampling rate for fixed head units. As you might expect, since the Japanese are the principal manufacturers of the rotary -head, video -cassette recorders, which they want to mate with PCM recording adaptors, they want to adopt a sampling rate which would not make these adaptors prohibitively expensive. The Japanese consider a 20-kHz bandwidth adequate to prevent deterioration of sound quality, including the effects of the anti-aliasing filter. It is this filter that costs so much, for the wider the bandwidth and the higher the sampling rate, the more complex and costly is the filter. There are other considerations involved in their early potential choice of the comparatively low sampling rate of 44.05594 kHz, such as length of recording time and easy conversion of the digitized audio signals into NTSC video signals. In fixed -head digital recorders, the Soundstream unit uses a sampling rate of 48 kHz, while the 3M/BBC recorder has a sampling rate of 50 kHz. Some who advocate an audio bandwidth beyond 20 kHz, are suggesting sampling rates as high as 100 kHz. The idea here is that the effects of the anti-aliasing filters at this rate would be above the audible range.

However, it is doubtful that either the Ampex or 3M digital mastering tape would be able to cope with the high sampling rate. Thus for a variety of reasons, the fixed head "professional" digital recorders seem to be leaning towards a sampling rate around 50 to 54 kHz. Well, enough said on this point. Here is a round-up of digital recorder activity at the 60th AES convention.

Digital Developments

The 3M people held a press conference just prior to the opening of the convention, and Dr. Marshall Hatfield, general manager of their Mincom Division stated that the 3M/BBC digital audio mastering system was "on schedule" and three systems would be in selected studios before the end of 1978. He also stated that continuous production of the digital recorders would begin early in 1979, at their Camarillo, California plant. The rather surprising news from 3M was that the 32 -channel pre -mix digital recorder and its companion 2/4 track mastering recorder, which were to be sold at a projected price of "under $150,000," would initially be available only through a lease -rental arrangement.

This is because 3M feels that the recorders represent a new technology, that further refinements are sure to evolve, and 3M must be responsible for their incorporation into the recorders. The financial arrangements are said to be $10,000.00 reservation/installation fee, monthly rental of $4,000.00, and a usage fee of $4.00 per hour. One assumes that on a three-year basis, this is equivalent to the original $150,000.00 purchase price. Dr. Hatfield is very bullish about digital audio in general, and reiterated that 3M is doing developmental work which it is hoped will lead eventually to consumer -type digital playback equipment.

The Soundstream digital recorder is currently not available on an outright sales basis. Instead, the recorder is part of a complete recording service wherein the unit and Soundstream personnel are in on the recording sessions, then offer editing services at their Salt Lake City headquarters, then ultimately take the recorder and the edited tape to the JVC Cutting Center in Los Angeles, where Stan Ricker can produce half -speed master lacquers. The digital recording service of Sound stream works on a royalty basis per record sold, with an advance against this royalty covering initial set-up, recording, and editing costs. Thus far, the Soundstream digital/half-speed disc master process has been used by Orinda Records for a recording of Diahann Carroll and the Duke Ellington Orchestra, and by Telarc Records for a recording of the Cleveland Wind Ensemble. The Telarc recording was being demonstrated on the Sound stream digital recorder at the AES and made a generally favorable impression. Incidentally, Dr. Tom Stockham, the head of Soundstream, was elected a Fellow of the AES at this 60th convention for his work in digital recording.

At the Mitsubishi exhibit room, they were showing their neatly packaged quarter -inch, fixed -head PCM recorder, which now is said to be priced at around $16,000.00, with availability by the fall of this year. Rumors continue to persist that they will have a PCM/Video-Cassette recorder combined unit for about $1800.00, which if true, would certainly be an incentive for the production of prerecorded PCM cassettes. Their unique laser/PCM disc system was again being demonstrated, but unfortunately at the time of my visit, a few gremlins in the system prevented another audition.

The pop -type music they were demonstrating was nice and clean, but did little to show the dynamic range/signal-to-noise capabilities of their PCM system.

Digital Miking

Genial Jim Kawada was presiding over the JVC demonstration suite, and was showing their ever -fascinating Qbiphonic sound system, and their spanking-new PCM adapter for their Vidstar video cassette recorder. The PCM unit is very attractively packaged, easy to operate with a minimum of controls. Jim was demonstrating a PCM recording of a solo piano, and while the piano was very clean with superb transient response, it was recorded far too closely with the mikes too far apart. The result was a clangorous sound with phase -shift causing some image jumping between speakers. Moral ... balances are just as important in digital recording as they are in analog! Also demonstrated was a big band recording, and while this too was a very clean sound, it just isn't the right material for showing off the important PCM attributes of dynamic range and signal-to-noise ratio.

The Technics room was loaded with digital surprises. Here too was a PCM adapter for their VHS rotary -head, video cassette recorder,. and again we found a very compact, easy to operate unit, with the usual snappy Technics styling. But the real stunner was a PCM fixed -head, open -reel recorder based on their RS1500 isolated loop recorder, using quarter -inch tape at a speed of 15 ips. However, the recorder has very special heads indeed. The record head is a common bias, thin-film magnetic head, made using photo -exposure techniques. There are a total of 60 tracks -30 for the left and 30 for the right channel-on the head, and the special fabrication permits a common bias to be used, with less than a fifth of the recording current necessary for conventional thin-film heads, making it possible to drive all tracks simultaneously.

The playback heads are magneto resistive effect heads. According to Technics, "the electric resistance of the nickel-iron ferromagnetic thin film components changes according to the strength of the magnetic field so that a high playback output voltage can be obtained even without a coil structure." Of course, with 60 tracks available, dropout countermeasures are emphasized with complete parallel processing. As stated by Technics, "based on recording the same signal on two different tracks (double writing)

and other methods, even if a section of the signal is missing, it will automatically be checked, corrected or compensated for, so that the reproduced sound will still be a precise replica of the original." Editing on this PCM unit will be possible, which is to be expected, but more importantly, record/playback monitoring is said to be possible. John Woram recorded some big band music at the old RCA studios in Hollywood using this new fixed -head PCM unit, and as played back in the Technics room under somewhat less than ideal listening conditions, the sound was strikingly "live" sounding, exceptionally clean, and singularly free of modulation noise.

Technics expects to announce price and availability of this PCM open -reel recorder at the Chicago CE S. Automatic Adjustment While we are at the Technics room, there were several other interesting developments in their isolated -loop analog tape recorders. There is now a model RS1520, which is essentially the same as the RS1500 introduced last year, but completely fitted with Cannon XLR connectors for input and output, plus front panel accessible bias and equalization adjustments. Then there is the RS1800, using the same isolated -loop transport, but with a larger record/playback amplifier section, which has a feature which is somewhat mind -boggling. How about a tape recorder on which you thread a reel of tape and then press the Record button? There is a red indicator light, and if you watch the VU meters, you'll see the needles hunt back and forth a bit, before settling on the highest reading, at which point, a green light comes on. What you have just seen is a recorder which has automatically adjusted for optimum bias for that particular tape! Finally, from the digital tape recorder front, was the aforementioned demonstration of the Sony PCM unit by Gene Czerwinski. Gene acquired a Sony PCM privately and a new Model 8300 Betamax and proceeded to make some jazz/rock type recordings in L.A. and Toronto. In all honesty they were of really excellent quality ... a solid bass end, very clean, and very quiet with a lot of presence.

As played back by Gene at his usual robust levels, it was an impressive sound.

As usual these days, in reporting on AES conventions, it is undeniable that digital doings take the lion's share of space, but as the fine cutting edge of the art, I feel this is justified. As has been evident during the last few conventions, automated mixing continues to advance in console construction, and at the 60th, the trend continued.

As for digital delay units, more and more companies are getting into the act. One of the pioneers in this field, Lexicon had one of the more interesting units in their Model 224 Reverberation Synthesizer. In its "Concert Hall Mode," two independent inputs are used to create the depth and space of three different sizes and shapes of halls. The user can control the reflectivity of the "walls" of the halls in three frequency bands with a digital parametric equalizer. With the "Depth Control," up to 200 milliseconds of apparent delay before the onset of reverberation can be programmed into the unit. Sonically, this was one of the best simulations of concert hall space I have heard thus far.

Recording Lathes

With all the talk of direct-to-disc recording these days, new disc recording lathes are welcome indeed. A new company called Cybersonics was showing a radical departure from the usual Scully and Neumann lathes. Very shallow in depth, utilizing a direct drive, servo -control turntable, with a hollow shaft for vacuum chip removal and lacquer disc hold-down, the lathe uses a shaft encoder to provide necessary information to what they call their Compu-Drive system for automatic -mode functions such as head drop, lead-in spiral, auto-tape start, lead-in termination, lock-out concentric groove diameter, head lift, and auto retract to rest position. Input to the Compu-Drive is from the preview head and provides updates of two to 18 times per turntable revolution for adjustment of pitch and depth. The whole lathe weighs in at just over 250 pounds, which makes it eminently transportable, and therefore a natural for direct -disc location recording. A micro -processor is said to be in the works, which will enable multiple units of the DM 2002 lathe to be electronically coupled for the generation of multiple lacquers. The DM 2002 can mount either a Neumann or Ortofon cutting head. The unit displayed used an Ortofon 732, but was not operational. It would be interesting to see some test cuts from this lathe, as it seems an interesting concept. The old pros at Neumann have come up with a new model disc cutting lathe, the VMS 80, which incorporates some of the ultra -refinements that have been derived from Neumann's research on videodisc cutting. Direct servo -loop drive for both turntable and lead screw, presentation of groove geometry by video screen as well as by microscope, built-in automatic banding unit, safety interlock command functions, and aircushion shock mounts are some of the niceties. All add up to new ease and precision in disc cutting in general and the cutting of long sides in particular. Importer of the new lathe, Gotham Audio, also showed their latest Magnetophon analog -tape recorder, the Model 15A, with up to 32 tracks on 2 -inch tape, optionally equipped with their Telcom C4 noise reduction system.

Willi Studer made a big splash with the introduction of his new A 800 multi-track recorder, with up to 24 channels, built-in autolocator and varispeed and his TLS2000 tape lock system. Otari came up with an 8-channel recorder using half -inch tape, and this will undoubtedly hold interest for the semi-pro market. As always, there were scads of interesting new equipment at the AES convention, but, I have had to trim much, in order to present the items of major import.

(Source: Audio magazine, Aug. 1978; Bert Whyte)

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