DIGITAL UP-MANSHIP (an article from Audio magazine, Jan. 1994)

[How have philosophies and technologies about “digital audio” changed since the early 1990s?]

For high-fidelity reproduction of recorded music, it is obvious that two requirements must be met. The first is for audio components capable of low distortion, wide frequency response, and wide dynamic range. The second is for a music storage and retrieval system capable of true high-fidelity performance. Since 1948, an entire industry has developed, based on the pursuit of many technologies devoted to fulfilling these two requirements.

Over the years, audio components reached very high levels of sophistication and refinement. Some would say that the performance capabilities of the very best audio components surpassed those of the various re corded media.

Record labels generally kept pace by constantly upgrading and refining technology in all aspects of record production. Technical one-upmanship was the game in selling records. Thus, we had new recording philosophies, with new types of microphones used in new configurations. There were advances in cut ting lathes, cutter-heads, and amplifiers. Various types of tape machines were employed in mastering, and some were specially modified. New ideas in plating and pressing technology were introduced, including the use of special vinyl formulations and the adoption of elaborate quality controls. Certain record companies created "audiophile" imprints. We had London/Decca's ffrr (or full frequency range recording), Bob Fine's "Living Presence" Olympian series at Mercury, RCA's "Living Stereo," and my own Everest Recordings (where we pioneered 35-mm magnetic film mastering). Indeed, labels went to extraordinary lengths to convince consumers that their recordings were unique and truly high fidelity. Of course, it wasn't all hype; there were indeed easily audible differences between the recordings of audiophile labels and those of mainstream labels.

Obviously my foregoing remarks cover the era of analog mastering and the vinyl LP. Although the digital Compact Disc is now in its second decade as the music storage system of choice, digital tape mastering has been used for a considerably longer time. In fact, well before the arrival of the CD in 1982, you may remember that many LPs had "digital recording" emblazoned on their record jackets. It was considered a selling point, even though a small group of audiophiles condemned the use of digital tape mastering.

Denon Records was experimenting with a 13-bit, "floating-point" digital tape mastering system as early as 1969, and actually issued some digitally mastered LPs in 1971. And I well remember that Decca demonstrated its proprietary digital tape mastering system to me in 1976, in London. Even back then, it was capable of both 16- and 18- bit recording and had very sophisticated error correction, including dropout detection, counting, and correction monitoring. In the U.S., 3M was developing its digital tape mastering recorder, and Tom Stockham already had working units of his Soundstream digital tape recorder. It seems incredible to me that I used Tom's digital recorder to master my Virgil Fox organ recording for Crystal Clear in 1977 and my Arthur Fiedler/Boston Pops recording in 1978.

IT SEEMS INCREDIBLE THAT SOME ENGINEERS WERE USING STOCKHAM'S DIGITAL RECORDER TO MASTER LPs BACK IN '77 AND '78.

Today we buy CDs or download digital files--which could have been made in any of more than 100 CD plants throughout the world--secure in the knowledge that they have been made to Philips/Sony Red Book standards, therefore guaranteeing certain performance parameters with respect to noise, distortion, frequency response, and dynamic range. But though the CD is a highly standardized product, the digital tape masters from which CDs are processed are made on a wide variety of digital recorders. It may be thought that, no matter the type or brand of digital recorder, in terms of performance they all operate on a level playing field. To a certain degree this is true, but it is now apparent that various digital recorders have certain performance differences; although subtle, these differences can influence a recording engineer to prefer a particular digital mastering system.

Currently, engineers can choose from a very broad group of digital mastering systems. Probably the most widely used digital recorders are the Sony 1610 and its updated cousin, the 1630. The latter is a two- piece system consisting of a U-Matic VCR (using 3 tape to store the digital signals) and a 16-bit digital processor. One of the attractions of the Sony 1610 and 1630 recorders is that they are part of a truly complete digital mastering system, including the all-important digital editors. The Sony 1630 is also the interface playback unit in the CD plants, feeding the digital music signals to the photosensitive glass master disc from which each CD will be processed. Whatever the format of digital tape master--R-DAT, S-DAT, DASH, etc.--submitted to a CD plant, it is transferred to a 1630 for processing. (The only time the 1630 is bypassed is if the CD plant accepts CD-R masters for processing.) Many engineers use professional R-DAT recorders from Sony, Technics, Fostex, and others. Although some engineers question the archival capabilities of R-DAT tape, it nonetheless is used for a great deal of digital mastering. Sony and Studer have DASH-format open-reel, two-channel dig ital mastering recorders, mainly for direct stereo recording. For multitrack digital re cording, Sony and Studer dominate the market. Perhaps the most ubiquitous units are Sony's 3324 (24 tracks) and 3348 (48 tracks). It is interesting to note that these recorders are 16-bit systems, with no provision for the 20-bit recording now so much in vogue. However, it is reported that a specially modified Sony 3324 provides 12 channels of 20-bit digital recording.

It should also be noted that although the video-based Sony 1630, all R-DAT recorders, and all DASH-format recorders have their own internal A/D converters, it is common practice among recording engineers to bypass these built-in A/D converters and employ external converters from Apogee Electronics, Wadia Digital, and others. This is especially the case if the engineer wants to produce 20-bit masters.

As to the future of digital recording, we can look forward to the Sony 9000, a magneto-optical digital disc recorder that operates at 16- or 20-bit resolution. There is even provision for 24-bit recording if someone will come up with a 24-bit A/D converter! As you might expect, all 20-bit (and above) recorders will require the use of Super Bit Mapping or some other dithering process in order for consumers to truly realize the benefits of these high bit-rate recording technologies.

Just as there were audiophile labels in the days of analog recording, there are audiophile labels in this digital era. London/Decca consistently turns out superb CDs of the highest fidelity, as it stays on the cutting edge of digital mastering with its updated proprietary recorders capable of 20-bit resolution. Another British label, Chandos, is well known for its audiophile recordings, employing as well a proprietary digital mastering system.

In the U.S., Telarc is certainly an audiophile label, notable for pioneering digital recording with the Soundstream mastering system. Nowadays, chief engineer Jack Renner is busily exploring new digital re cording technology and often experiments with different A/D converters. He has a proprietary Telarc/UltraAnalog digital processor and is doing 20-bit recording using a Mitsubishi PDX-8620 open-reel digital recorder.

IF ENGINEERS DIDN'T HAVE A SENSITIVITY TO MUSIC, THEIR CDs WOULD MERELY BE "TECHNICALLY CORRECT."

Craig Dory, the venturesome head of Dorian Recordings, is experimenting with new digital mastering equipment such as the exotic Nagra D, which records open-reel tape with an R-DAT head! I also Understand he has been doing direct-to-hard- disk recording on a Sonic Solutions system.

High on the list of audiophile labels is Delos, where colleague John Eargle employs a Fostex D-20 R-DAT digital recorder to produce, in my opinion, the finest classical CDs available. Of course, it is not just the choice of recorder, but the whole of John's recording technique-especially his unerring sense of orchestral balances, hall perspectives, and musical textures-that makes his recordings so outstanding.

The counterpart to John Eargle in the jazz field is Tom Jung and his dmp label. Tom has an incredibly keen ear, and he uses the most advanced equipment: FM Acoustics custom mike preamp, Wadia 4000 A/D converter, and Yamaha DMR8 S-DAT recorder (an eight-channel unit affording 20-bit resolution). His recordings are immaculately clean and have stunning dynamics. Here, too, it is not merely cutting edge digital recording that matters, but also Tom's musical perceptions. and his uncanny ability to achieve just the right instrumental balances.

Engineers of the audiophile labels can point out the best qualities (and the artifacts) in the digital mastering system they have chosen, but if the same engineers didn't have the requisite knowledge of microphone types and how they are deployed, a thorough grasp of hall acoustics, and above all a responsive sensitivity to music, their recordings would merely be "technically correct”.

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