With the continuing dynamic growth of the professional audio industry, it has become something of a cliché to report that every Audio Engineering Society convention is "bigger than ever." This certainly was the case with the 61st AES convention at the Waldorf in New York, November 3-6.
As usual, the Waldorf's ballroom was filled to capacity with exhibits, and this year the stage area and all the boxes in the upper balconies of the ball room were also pressed into service.
Along with the demonstration rooms on the 12th floor, the conventioneer was confronted with a truly mind-boggling array of audio equipment.
Needless to say, as has been the case for the past few AES conventions, digital technology was the dominant theme. However, even the anticipation of this situation did not prepare us for the onslaught of activity in this field. Any visitor to this 61st AES convention, after having been exposed to all the glittering new digital recording equipment on display and listening to the many papers on digital technology, would have to conclude that the digital revolution isn't coming ... it is here! Thus, I make no apology for this AES convention report being mainly oriented to the "digital domain." It had been widely anticipated that at this 61st AES convention, the standards for digital recording would be established, or at the very least, close to resolution. Unfortunately, some unforeseen complications and procedural problems, not necessarily technical in nature, have put the standards deliberations on "hold" for the present. However, a "Technical Committee for Digital Audio Engineering" has been formed to ensure an ongoing ex change of data on digital technology which, it is hoped, will make a significant contribution to the resolution of the standards problem.
Of course, digital technology has been evolving for some time now, and except for certain proprietary aspects of the technology within various companies, most digital information is on a "shared access" basis among audio engineers. Thus, by happenstance and coincidence, the digital recorders which have appeared share many common features. For example, among the so-called "professional" stationary-head digital recorders, they all use 16-bit systems. The 3M, Soundstream, and the proposed Ampex digital recorder all have opted for a 50K per second sampling rate. They all give very cogent, but remarkably similar reasons for the rationale in their choice of sampling rate. The Japanese, on the other hand, whether their digital recorders are the ubiquitous helical scan variety or the few stationary head models that have appeared, still cling to their 44.056K sampling rate and its tie-in with the NTSC TV signal. Up until quite recently, all the helical-scan PCM recorders based on the various VCR formats have used a 13-bit, with 1 parity bit, nonlinear encoding setup.
Now, in the interests of better signal to-noise ratio and less distortion, the new Japanese "standard" appears to be a 14-bit linear encoding system. It would probably be correct to all these 14 bit/44.056K sampling rate PCM recorders as digital machines for the consumer market.
---3M Digital Editing System
Digital Evolution
Now let us take a detailed look at the digital recording equipment on display at the Waldorf. The 3M digital recording system has been described previously in these pages. It is a 16-bit/ 50K sampling rate system. At the Waldorf they were showing updated versions of the 32 channel on one-inch tape mastering recorder and the 2/4 channel on half-inch mix-down machine. The four systems promised to recording studios by the end of 1978 are said to be on schedule. Most importantly, 3M unveiled its electronic editing facility for the digital recorders.
The 3M programmable electronic digital editing system was engineered jointly with Inter-technology Exchange (ITX), Ltd. of Hollywood. The editing console consists of a video screen, teletypewriter keyboard augmented with special function keys, and remote controls for the 32-channel master and 2/4 channel mixdown recorders. In use, the editor selects the rough edit point by listening, then looks at enlarged visual representations of the sound amplitude on the video screen.
The display first shows 40 samples on either side of the tentative edit point and then the point is refined further by a so-called "zoom" function. With time-code control of edit points and microprocessor control of execution accuracy to within 20 microseconds (!), elaborate inserts and assembly edits are possible. There is also the great ad vantage of being able to "preview" hear the intended edits before their actual execution.
The 3M commitment to a complete digital mastering system was further evidenced by their announcement of a disc lathe preview unit. Using a random access memory, time generator, and digital-to-analog converters with a signal delay adjustable up to 1.3 seconds, the device delays a set of digital signals from the master recorder while analog signals proceed to a conventional computer lathe controller that optimizes groove pitch and depth. The important thing here is that the delayed signals remain in the digital domain, maintaining their integrity until the end of the delay, thus with no degradation of quality.
Dr. Tom Stockham's Soundstream digital recorder was the pioneering unit in the field. It still is a 2/4 channel unit using 1-inch tape and in its latest embodiment is a 16-bit/50K sampling rate system. Editing is done at Soundstream's Salt Lake City headquarters.
The system is in frequent use by a number of record companies, as a specific record session service under direct control of Soundstream. Sound--stream did not have a demonstration room at this convention, no doubt feeling that by now the system is quite well known, and some records made with it are already on the market.
Sony Surprises
One of the big surprises of the convention was the high degree of involvement by Sony in digital recording. Of course, they have pioneered in the consumer-type helical scan VCR recording with their PCM-1 digital encoder/decoder. I have recently used one of these units with considerable success. At the convention they were demonstrating their "big league" PCM unit, the Sony 1600. The 77-pound PCM-1600 is a 16-bit linear quantization system with, however, the familiar Japanese 44.056K sampling rate. The PCM-1600 is used with the Sony BVU 200A helical scan 3/4-inch U-matic VCR.
Electronic editing can be performed using the Sony BVE-500A videotape editing console. By using two of the VCR units with the video editor and the PCM-1600, pitch and depth control are possible with disc cutting laths.
The significant thing about all this is that the PCM-1600 and associated equipment is a system now in production, not a prototype. Price of the system is said to be around $46 thousand. Not content with this, on the stage of the Waldorf ballroom Sony had set up their imposing new 24-channel proto type PCM-3200 stationary head digital recorder. Actually this is one of a series of recorders in which 2/4 channel versions on 1/4-inch tape, 8 channels on 1/2-inch tape, 16 and 24 channels on 1-inch tape, and 32 and 48 (my gawd) channels on 2-inch tape will be avail able. All are 16-bit linear quantization systems, but a real surprise is that there is a switch-selected choice of a 44.056 or 50.35K sampling rate. Sony is covering all bases! The number of tracks on these recorders is greater than the number of channels, as they use two tracks per channel to allow phase modulation and proper redundancy, plus two analog audio tracks and one SMPTE time code track. The SMPTE track will aid in electronic editing on the deck and multi-deck synchronization. A tape speed of 15 ips is said to provide up to 120 minutes of recording.
As if all this activity in digital recorders wasn't impressive enough, Sony capped this by introducing a digital audio mixer. Initially it is an eight-input, two-output small unit, but Sony plans larger units all the way up to 48 channels! It is designed to mix 16-bit linear quantized digital signals with no analog process involved. It has the usual slider fader controls, echo send and receive facilities, and analog plasma bar-graph displays for level. Here again, sampling rate is selectable be tween 44.056K and 50.35K with, how ever, a maximum clock rate of 56K.
The reason for the echo send and receive is that Sony has also introduced a digital reverberation system.
The DRX-1000 has a built in micro-computer that allows programming of four different reverberation modes.
The unit accepts digital signals directly and adds reverb directly. It has initial delays up to 100 milliseconds, with reverb times as long as 20 seconds. The mixer will interface with digital equipment with sampling rates up to 55K. It will interface with analog equipment and Sony's new A-to-D and D-to-A ADA-1601 two-channel converter also introduced at the convention. It is obvious that Sony is aiming for the total digital recording facility and, at this convention, they have shown that they are really serious about digital technology.
Sony DAD-1 Digital Disc Player
One further bolstering of this idea was provided by the introduction of their DAD-1X digital audio disc. The system uses a one-sided reflective disc revolving at 450 rpm and is scanned by a low-power, helium-neon laser. The disc system is 16-bit linear-encoded PCM, with 95-dB dynamic range, and less than 0.03 percent distortion. Be cause of a new high density "run length limited code" system, the disc can play for an astounding 21 hours on one side.
Ampex has been keeping a low pro file on digital recording, although good reason told you that they must be working on a system. Ed Engberg, Ampex engineer, gave a paper on a so called "Proposed Digital Recording Format," which, not unexpectedly, opted for 16-bit linear quantization and a 50K sampling rate. Indications are that the ATR-100 might be modified as a digital mastering machine.
Plans for any multi-channel digital recorder are unknown at this time.
JVC was demonstrating its new 14-bit PCM unit with its Vidstar VCR, and it was very clean-sounding with some pop-type music. They are reportedly going to be demonstrating their capacitance-type digital disc system at the Winter CES in Las Vegas.
Digital Discs
Along with a prototype model of their RS-1800 30-ips automatic bias and equalization adjusting tape recorder, Technics was demonstrating their SH-P1 PCM digital encoder/decoder with the Panasonic VHS/VCR deck.
Yours truly recorded the digital tape for them, the Marlboro Festival players in Stravinsky's l'Histoire de Soldat, and I am pleased that it elicited much favorable comment. I am hopeful it will be heard at the Winter CES via their VISC digital disc.
Pioneer and MCA/Universal were demonstrating their digital disc version of the video disc Pioneer manufactures in Japan for industrial users. Not much info on it, other than it's another laser-scan system with 30 minute playing time per side and dynamic range 85-90 dB. Finally on the digital frontier was a paper by Philips on its compact laser-scan disc affording 90-dB dynamic range and a playing time of one hour per side. Oddly enough, it is not supposed to be compatible with their laser-optical video disc.
When I was in London recently re cording the London Philharmonic Orchestra, Arthur Haddy, the Technical Director of Decca Records, was kind enough to invite me and Mrs.
Whyte to a private demonstration of Decca's new digital tape mastering system made in their own laboratories at Finchley. Bill Bayliff, general manger of the Decca recording studios, and Tony Griffiths project manager at Finchly, were in attendance to explain matters and, in fact, were to attend the AES convention as well. I have been asked not to reveal certain details, but I can tell you it is a 16-bit linear quantization system, and the sampling rate is confidential. It uses a professional one-inch helical scan transport, has the ability to monitor off the tape, has, it is claimed, "100 percent dropout correction" (!), and very importantly for a record company ... complete "on session" electronic editing facilities. We heard some Ashkenazy Mozart from Kingsway Hall, plus an operatic recital from Walthamstow, and both were absolutely superb in terms of clarity, cleanness, and wide dynamic range. Furthermore, edits were performed right before our eyes and ears, to perfection I might add.
With it taking sometimes a couple of years to assemble operatic casts, the on-session editing ability is vital to such projects. Obviously, our British cousins are very much into the digital scheme of things.
Yes, Virginia , there is a thing called analog audio, and there were some interesting new items at the AES convention which we will discuss next month.
(Source: Audio magazine, Feb. 1979; Bert Whyte)
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