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All information in these pages is copyright (c) 1989-2003 by Roger Nichols. All rights reserved. Permission for personal reference only, and may not be reproduced by any method without written permission.

I Can’t Keep Up With All The Formats III
by Roger Nichols

PD, or not PD.
Continuing on with our format coverage, we will start with Mitsubishi’s foray into the future of digital audio. In 1983 I got to use the first Mitsubishi X-800 32-track one-inch digital machine, and their X-80 reel-to-reel two-track digital recorder. The first project to be recorded on the X-800 was John Denver’s One World featuring Bob Marley’s band The Wailers, recorded at Criteria Recording Studios in Miami. We mixed to the X-80 two-track and mastered with Bob Ludwig at Masterdisk in New York.
The second-generation digital machines had ten times better error correction and all of the tracks were on the same head to avoid the error prone physical adjustments that needed to be done with the 3M machines. Mitsubishi later improved and shrunk the 32-track machine with the X-850, and later the X-880 32-track machines. Otari licensed the PD (ProDigi) format from Mitsubishi and produced the D-900 machine, which would record and play Mitsubishi 32-track tapes.

The original X-80 two-track used a sample rate of 50.4kHz and 1/4” tape. The sample rate was later changed to 48kHz as the emerging standard for professional sample rates. George Duke and I had the only two X-80s for a while, and some of our early tapes were done at 50.4kHz. Mitsubishi later replaced the X-80 with the X-86, and then the X-86-HS. The HS version was capable of recording at 88.2kHz and 96kHz. The Rikki Lee Jones Flying Cowboys CD from 1989 was recorded on the X-850 and mixed to the X-86-HS at 96kHz. There was an option that allowed the playback of incompatible X-80 tapes on an X-86 or X-86-HS.

Nashville was the Mitsubishi capital of the world, with the highest population of 32-track machines on the planet. The record companies and studios opted to standardize with one format so that projects could easily migrate from one studio to another. If you wanted to be a competitive studio in Nashville, you had to have an SSL console and a PD format (Mitsubishi or Otari) digital 32-track.

Sony, No Baloney
Sony introduced the DASH format machine in 1984. The DASH format PCM-3324 was 24 digital audio tracks on half-inch tape. I worked on the first DASH session at A&R studios for the Cotton Club soundtrack. DASH machines started popping up like wild mushrooms. A pretty stable machine with a 50% savings on tape cost (half-inch instead of one-inch tape).
Sony owns most of Tascam, so it was no surprise that Tascam jumped on the DASH format bandwagon, introducing a low cost ($90,000) version of the 24-track DASH machine. The Tascam machine did not share enough of the market and finally discontinued the machine.

In 1989 Sony delivered the PCM-3348 DASH machine with 48 tracks of digital audio, still on half-inch tape. It turns out that the DASH format had always left space on the tape for 48 tracks, and they left half of the tape blank for the 24-track version. A 24-track tape will play on a 48-track machine, and the first 24 tracks of a 48-track tape will play on a 24-track machine.
Studer licensed the DASH format from Sony and built their own 48-track DASH machine. Lots of studios bought Studer 48-track machines, but most of the ones who did already owned a Sony PCM-3348.

Sony also built a two-track DASH machine using 1/4” tape, the PCM-3402. Sample rates were 44.1kHz and 48kHz.

DASH and PD Today
Sony has introduced the next level of DASH machine, the PCM-3348-HR. The HR stores 24bit data for each of the 48 tracks. The machine still uses half-inch tape and will play and record any previous DASH format tape. But in 24bit mode the tape travels at 45ips instead of 30ips.

Editing Digital Audio Tape.
Editing digital audio was an experience all its own. With analog tape you could rock the tape back and forth over the heads slowly and hear the audio. This made it easy to find the beginning of a kick drum or snare drum hit. With digital audiotape, the tape cannot be hand rocked. The tape has to be running at full speed before the bit stream can be decoded, and there is a delay before the audio is spit out of the converters. This makes it kind of hard to accurately select your edit point.

The 3M machines allowed you to edit in the video style, except that the 3M machines use their own internal synch address codes and an edit controller that plugs in between the two machines. That is, you pick the edit point on the source machine, pick the edit point on the destination machine, and then hit the preview button. The machines pre-roll, the destination machine plays, and at the edit point the destination machine switches to input. If you like the edit, press the edit button and the destination machine goes into record at the edit point. If you need to trim the edit point the machine being trimmed will play before the edit point and mute, or play nothing and then un-mute audio at the edit point. With this method you can trim the edit points in one-millisecond increments until you get just what you want.

The Mitsubishi and Otari machines are synchronized with the remote control and work in a similar fashion. The Sony machines use DASH lock for synchronization, which allows one-millisecond accuracy. The PD machines and DASH machines also have an analog track where you can record a copy of whatever is important for cueing of the edit point. Since it is an analog track, you can scrub the audio to select the edit point. In scrub mode the delay is taken into consideration for the calculation of that edit point.
Akai, ADAT, DA-88

The term MDM (Modular Digital Multi-track) describes the new crop of small videotape based digital audio multi-track machines that started showing up about 1989. The first of these machines was the Akai 12-track digital recorder. The Akai 12-track used 8mm videotape to record digital audio. Tracks were recorded in pairs, because the chipset used for encoding and interleaving came from the newly introduced DAT machines. Six pairs of tracks were recorded on the 8mm videotape which ran at six times normal videotape speeds allowing 20 minutes of recording on a two hour tape. I recorded a couple of projects on them, but the error count got very high very quick. Also, because of the DAT method of recording tracks in pairs, whenever you punch in on a track 1, track 2 is taken off the tape and re-recorded. If there happens to be a playback error during this operation, the clicks will be recorded on the track that you are not even recording on. Nobody liked this very much, and the machine quickly fell out of favor.
Alesis introduced the ADAT eight-track digital recorder shortly thereafter. The ADAT recorded eight tracks on VHS tape. The two-hour VHS tape only lasted 40 minutes because the tape and head speed was three times the normal video transport speed. ADATs sold like hotcakes. Every major studio and every project studio in the world jumped on the ADAT bandwagon. Multi-track digital recording for the masses was becoming a reality.

Not to be out done, Tascam introduced the DA-88, which was an eight-track recorder based on 8mm videotape. To keep the recording time up around two hours, the DA-88 used narrower heads, closer track spacing, and higher data density. Until tape manufacturers caught up, the error rate on DA-88 machines was higher than ADATs, but the longer recording times were a big plus, especially when recording live concerts.

Because of the Sony/Tascam relationship, Sony introduced a DA-88 compatible machine. When higher bit rates hit the scene Sony dropped their machine and Tascam produced the DA-78 and DA-98 24bit machines. ADAT built a professional version of the ADAT called the M-20, as well as three new semi-pro models that recorded 20 bits, but because of the encoding method, 24bit was beyond the ADAT capability. Studer licensed the ADAT format and built a professional machine like the M-20.
ADAT sales started falling off and Alesis acquired new owners during the summer of 2001. Tascam is still producing DA-xx series machines, but tape based machines seem to be winding down with the introduction of bigger, faster, cheaper hard disk based systems. Tascam and Alesis both have 24 track hard disk based recorders on the market. Mackie skipped over the tape based machines, but has introduced a 24-track hard disk recorder. We will cover these in the final installment next month.
Honorable Mention

Remember that the Sony PCM-10, PCM-F1, PCM-1610, PCM-1630 and the DBX system were also videotape-based systems, so the technology had merit. There was a company in Hollywood California that built a modified PCM-F1 that recorded four tracks on videotape. There was also a company that made a video recorded that used DAT tapes. Hey, turnabout is fair play! DAT machines use rotary head technology to record the data on tape as well.
All formats of helical scan machines seem to be on the way out rather quickly. Stationary head machines are hanging in there because of the professional use, but the handwriting is on the wall, random access for all. Even so, you will surely run across one of these formats sooner or later. Recognizing what you have to deal with will be a good head start on finding the right machine to play it back.

Next month will complete this format coverage with inclusion of all the new formats on the market, and what the outlook is for the future. Someone has to keep some of these machine around for a while to be able to play back tapes that were recorded during the ancient history of digital audio (the ‘80s). By the looks of my garage, I guess that would be me.