DASH WITH PANACHE

The 76th Convention of the Audio Engineering Society was held October 8th through 11th, 1984, at the New York Hilton Hotel. This was the second year at this venue, and the hotel remains starkly commercial, making me yearn all the more for a return to the gracious and civilized ambience of the Waldorf. No doubt spurred by the ever-growing interest in digital audio, attendance was gratifyingly high.

While there were no industry-shaking breakthroughs, many interesting new products were displayed.

---Sony PCM-3102

You may recall that in last January's issue I noted that a consortium of Sony, MCI, Studer, and Matsushita had agreed to the adoption of DASH (Digital Audio Stationary Head, a digital audio recording system. I explained the system and the number of tracks possible at 71, 15, and 30 ips on quarter and half-inch tape. All digital recorders that use the DASH system are supposed to be compatible with each other. At this convention, both Sony and Studer introduced their own versions of DASH digital recorders. While similar, there are certain differences, which prompted some less than friendly remarks from respective company spokesmen. As reported in the Pro Sound News Daily (a convention newspaper), Studer claimed that "Sony's guidelines for DASH are 'too restrictive' " and that they "have 'differing views' about components that should be features in DASH machines." "One difference," said PSND, "is that the Sony system is driven by an auxiliary track, while the Studer system is driven by a digital track."

The Sony PCM-3102, a two-channel DASH recorder operating in the slow (7 1/2-ips) mode, affords 2 hours of digital recording on quarter-inch tape on a 10 1/2-inch NAB reel. It uses 16-bit linear quantization with sampling rates switchable between 44.1 and 48 kHz.

The PCM-3102's two analog tracks can be used for recording in the event of a failure of digital recording capability.

Digital and analog tapes are recorded in-line, and this permits manual cueing and razor-blade editing. An SMPTE time-code track is provided to allow accurate synchronization with film and video applications.

The Studer D820 also operates in the DASH slow mode and has the same sampling frequencies. The D820 uses what are claimed to be virtually "adjustment-free" in-line ferrite heads in a die-cast head block. Twelve in-line tracks are recorded on the quarter inch tape (eight for digital audio, one for time code, one for reference data and two for digital cueing, one of which can later serve as Compact Disc sub coding). Two-hour recordings are possible on a 10 1/2-inch NAB reel and in excess of 4 hours on 14-inch reels.

Control of the D820 is through a network of microcomputers under supervision of a master control. As with the Sony PCM-3102, the Studer D820 can also be used as an analog recorder.

The D820 machine features newly developed A/D and D/A converters and audio filters. Time-code synchronization is also available, and both electronic and razor-blade editing are similarly possible.

-------Studer D820

Both the Sony and Studer DASH recorders are technical tours de force, with Matsushita's machine still waiting in the wings. A number of companies which manufacture digital recorders did not join the DASH ranks. One of them, Mitsubishi, needled the DASH group in a prominent ad in the convention Daily: "Mitsubishi, 74-DASH, 0" the ad proclaimed, stating the company had delivered 74 of their X-80 digital recorders against no deliveries of a DASH machine. However, in another ad, Mitsubishi goofed in stating they had "the only 32-track digital recorder." Obviously, they forgot the 3M 32 track recorder, which is still very much alive. (My recording associate, Frank Dickinson, is currently using four of them in his Digital by Dickinson recording service.) In spite of the glamour and excitement of digital recording, there were a surprising number of new analog recorders introduced at the convention.

Although most classical recordings these days are digitally mastered, apparently there are enough applications for high-quality, two-channel analog recorders to warrant the manufacture of new models. Of course, it must be said that with the availability of microcomputers and other advanced technology, these new analog recorders have performance parameters and operating conveniences far beyond the best analog machines of just a few years ago.

A case in point is Studer's new A820 analog mastering recorder. This unit, which accepts 14-inch reels, has a completely new transport with multiple microcomputers for control and monitoring of all functions. Approximately 40 user functions can be programmed, and there are new phase-compensated audio electronics. Inputs and outputs are available with either transformers or advanced active balancing circuitry. Such parameters as bias, level, EQ, etc. are set and stored digitally.

Options for the A820 will include center-track time code and a serial interface for external computer control. The price for a two-channel, quarter-inch A820 in a console will be approximately $10,000, with delivery slated for mid 1985. An A820 handling half-inch tape will also be available.

Directly competitive with the Studer A820 is Otari's MTR-20 mastering recorder. This, too, is a very modern machine utilizing microcomputers for many functions. It offers tape speeds of 30, 15, 7 1/2 and 3 3/4 ips, with switch able NAB/ICC/AES record and playback equalization. A really nice feature is the record alignment system: Record level, bias level, high- and mid frequency EQ, and phase compensation are automatic. Eight record alignment memories store setups for two tape formulations in each of four speed/EQ combinations. SMPTE time code is available, as is an optional interface for external computer control.

The MTR-20 is available in two-channel, quarter-inch and two- and four channel, half-inch configurations.

------Tandberg TD50

Still another competitor in this area is Tandberg's TD50, a professional, quarter-inch mastering recorder. Tandberg has a long history of producing excellent consumer open-reel recorders, but this is their first entry into the true professional recorder market. The design of the TD50 incorporates some innovative ideas. For example, all mechanical components of the transport are mounted directly to a 10-mm hick plate of special Alcoa "Alca Plus" aluminum alloy. This alloy is molded by a proprietary process which is claimed to result in exceptional flatness and a memory that enables the alloy to return to its original shape after stress. Tandberg also uses a microprocessor for many control functions, with SMPTE time code and an external computer interface available. The TD50 has 15, 7 1/2 and 3 3/4 ips tape speeds, and it can use 101-inch reels or 12nch pancakes. The three-speed capstan motor is controlled by a quartz reference oscillator. Settings for bias, level, and EQ are controlled by the microprocessor. Tandberg is particularly proud of the TD50 electronics: Only discrete components are used (no ICs), with a minimum number of polyester capacitors in the signal path and minimum use of negative feedback.

The head block is also made of the "Alca Plus" alloy, and tape guides are solid ruby. The TD50 is obviously a well-thought-out machine, built to withstand the rigors of professional recording. Price will be around $8,000.

--------Tandberg TCD910

Tandberg also introduced the TCD910, an elaborate professional cassette recorder, and the TCCR530 computer-controlled cassette recorder. The TCD910 should get a warm welcome from studio engineers who have been frustrated by consumer cassette recorders.

One last item before I close: The Kurzweil 250 synthesizer. One of the hits of the convention, this is a mind boggling instrument which, in the hands of an expert, can not only create the exotic sounds normally expected from a good synthesizer but give very lifelike, believable simulations of musical instruments. The 250 has an 88 note keyboard, as does a normal piano, and it processes 12 channels with a dynamic range of over 100 dB. The complexity of the microprocessor system is staggering. As Kurzweil so whimsically puts it, "resident instruments" include concert grand piano, violin, viola, cello, and bass string sections; plucked acoustic bass, snare drum, bass drum, crash cymbals, and other percussion instruments are available. There's also trumpet, baritone horn, valve trombone, nylon-string acoustic guitar ... I could never describe all of the effects! The Kurzweil 250 comes with 40 factory-installed keyboard setups, and many more are user-programmable. The unit may be interfaced with an Apple Macintosh computer.

It is the sounds the 250 makes that are so remarkable. The piano is outstanding, with sharp, precise transient attack and a well-developed harmonic structure. The same can be said for percussion. Trumpet and horn are extremely realistic, again with good harmonic structure. Of course, the electronic players in this orchestra can produce dynamics and explore frequency extremes beyond the capabilities of mere men! Up to six layers of sound can be programmed, and it was quite startling to hear a single demonstrator play piano, with percussion accompaniment, plucked string bass, etc. The 250 is an incredibly versatile instrument, costing slightly over $10,000. I don't know beans about playing an instrument like this, but I do know that I would have a great time just diddling around with one!

(adapted from Audio magazine, Bert Whyte)

= = = =