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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.

How To # 384

By Roger Nichols

I wrote a review of Digidesign's new Digi 002 system for EQ that appears elsewhere in this issue. I like to review items that I can actually use on sessions that I am working on. In this real world environment it is much easier to find the strengths and weaknesses of a new product. Over the years I have purchased many software packages and audio gear that looked good in the reviews, and said everything I wanted to hear on the box, but after a week or to of trying to interface the equipment, or put the software features to work, I found some of the claims to be exaggerations, at best.

As an example of my frustrations, let me recount an earlier story.   I used to use a page layout program called RagTime (finally available again). RagTime would allow you to have text at any angle across the page, even vertically. When the text was at an angle you could easily click on the text and edit it, change size, change font, and change style while the text was still at an angle. After RagTime became extinct I bought every single page layout program there was, all of them stating that they worked with vertical text. None of them could actually edit the text while the text was at an angle. You had to enter the text horizontally, rotate the text to view it at an angle, rotate the text back to horizontal, edit, and then rotate it back to the position you desired and view it again. In some programs you had to render the rotated text as a TIF object before you could view it, then delete it and start over if you wanted any changes. It was never as easy as looking at your 50% gray text at a 33 degree angle across the page, and change all of the parameters to look the way you wanted it to look in a WYSIWYG (What You See Is What You Get) fashion. It took almost 15 years for other page layout programs to offer this feature.

The same happens with audio hardware. The new piece of gear does everything except the one thing that you needed it to do, almost all of the time.

002 Saves the Day

I worked on a project that was recorded at a studio that had a Pro Tools Mix3 system. One of the songs ran up against the 64-voice limit. The plans were to record live strings and horns on this song. We made a slave session that contained a two-track mix of the song so there was plenty of room left over for the additional recordings. We recorded the strings and horns and then planned to make a sub-mix of those 24 tracks and import them back to the original song. Great idea!

Once we started working on the final mix of the song, it became clear that we wanted more control over the internal mix and positioning of the strings and horns. We needed the individual tracks, but with a 64-voice limit, and no Pro Tools HD system available, what were we to do?

Well, we brought in a Digi 002 system and opened up the slave session under Pro Tools LE running on a Ti Powerbook. Since we needed the two Pro Tools systems to sync together, we went back to the TDM system and recorded the time code out of the USD box onto one of the Pro Tools audio tracks. We then imported that track into the slave session, resaved the session, and then opened the session on the Digi 002 system. We connected ADAT optical in and out of the Digi 002, fed from an ADAT Bridge connected to the TDM system. Following along so far? Good.

Since we were not going to use the sub-mix tracks in the TDM system, we could free up enough voices for four stereo aux inputs. One stereo input for the string sub-mix, and one stereo aux input for the horn sub-mix fed from Digi 002 outs 1-2 and 3-4, respectively. We wanted to be able to control the reverb sends from individual tracks on the Digi 002 system, so we routed the string sends to physical outputs 5-6 and the horn sends to physical outputs 7-8. These channels made their way to the TDM system via the ADAT optical cables. In the TDM system, aux 5-6 and aux 7-8 were fed to the reverbs connected to the TDM system. I was using the tc6000 hardware reverb connected to hardware I/O on the TDM system. Now when I wanted more reverb on just the French Horn, I turned up the send on the French Horn track on the Digi 002 session, the signal traveled over the ADAT optical cable to the TDM system, through the TDM aux output to the tc6000, and back through the aux return on the TDM system to become part of the final mix.

The Digi 002 was synced to the ADAT optical input, which made the TDM system the master. The SMPTE track was routed out one of the analog connections on the Digi 002 console and connected to the SMPTE input of the USD sync box connected to the TDM system. We used the transport controls on the Digi 002 console to locate to the various sections of the song, and for Play and Stop commands. The TDM system was the time code slave, even though the TDM system was the clock master. It all worked perfectly.

One small speed bump. Bounce-to-Disc could not be used because the systems would not lock together during this process. We had no more tracks available on the TDM system to record the mix back to Pro Tools, so we routed the mix digitally out of the TDM system, through the ADAT optical connection to the Digi 002 system, and printed the mix on two new tracks on the Digi 002.

Alternate Sync Method

I used SMPTE to sync the Pro Tools TDM system to the Digi 002 because that is what I am used to doing. Because the Digi 002 does not support SMPTE, I had to cheat and use the Digi 002 as the time-code master and make the TDM system chase. You could sync the Digi 002 to the TDM system by using MTC (MIDI Time Code) as an alternative. You could then have the Digi 002 system act as the slave and chase the TDM system.

On the TDM system you go into the Session Setup window and select Generate Time Code using MTC. On the Digi 002 system all you have to do is place Pro Tools LE in chase mode by clicking on the clock icon in the transport window. MTC coming from the TDM system will trigger the start of the Digi 002 system. You must, of course, have a MIDI connection from the USD interface to the Digi 002 console.

Trigger vs. Chase

Just a quick explanation of the difference between actual SMPTE chase and Triggered sync.

With SMPTE chase mode, SMPTE time code provides the time reference and the speed reference. If the SMPTE time code slows down, the chasing machine must slow down also. If this does not happen, you lose sync. This is the common sync method if you are chasing an analog machine.

Trigger sync looks at the SMPTE time code and derives the position of the master tape. The Pro Tools slave system starts playing instantly at the reference time. Once Pro Tools (or any digital DAW or Tape machine) starts, it no longer looks at SMPTE for speed. The speed reference comes from word clock or the digital sync (ADAT optical or S/PDIF connection) between the master and slave device.

Even when using SMPTE, digital audio workstations and digital tape machines use word clock or the digital sync connection to stay synchronized after the machines are locked together. So, trigger sync is not a less accurate method of locking digital devices, it is the ONLY way to lock digital audio devices. Therefore, MTC trigger sync is just as good as SMPTE sync in most cases.

Well, there you have it. Those of you who were complaining about Digi 002 not having word clock don't need to worry. You can still sync Digi 002 to anything you want, and trigger sync will get everything locked together, whether it is Digi 002, Nuendo, Digital Performer, Cubase SX, or anything else you can drag out of the closet. (Is it legal to say drag and closet in the same sentence?)