Digital Performer 5 and later include apps called MOTU SMPTE Setup (for FireWire MOTU interfaces) and MOTU PCI SMPTE Setup (for systems with PCI-424 cards) — they’re in your Mac’s Applications folder, and they let DP send SMPTE time code to any available audio output on a connected interface.
Step 1. In the main rig’s SMPTE Setup window, set the Destination (under “Generator”) to the first analog output of your MOTU audio interface. Make sure the “Generate from sequencer” button is lit, and that the overall Clock/Address setting is “Internal/Internal.”
Step 2. In the backup rig’s SMPTE Setup window, set the SMPTE source (under “Reader”) to the first analog input of its MOTU audio interface. Make sure Freewheel Address and Freewheel Clock are set to “infinite,” and that the overall Clock/Address setting is “SMPTE/SMPTE.” Make sure the two Frame Rate settings match.
Step 3. On the backup rig, ensure “Slave to External Sync” is checked in DP’s Setup menu. Select “Receive Sync” from that same menu to go to a preferences page. There, choose “Sampleaccurate” as the type of sync. Just under the menu shown, there are frame rate options. Match the frame rate to Steps 1 and 2. 
Step 4: You could use the SW8’s 1/4" inputs, but with a couple of short adaptor snakes, you can cut the spaghetti factor. Connect lines 1–8 of the snake to outputs 1–8 of the main MOTU UltraLite, then secure the snake’s male DB25 plug to Input-A on the SW8. Then, do the same with the backup UltraLite and Input-B on the SW8. Now, you’ll have seven SW8 outputs to send to the main PA for mixing. The SW8 listens for channel 1 on the A inputs to drop out — if that happens, switching all channels over the B system is automatic and instant. You might hear a slight pop, but otherwise you’ll never know anything went wrong. More importantly, neither will the audience!
The answer is to live by the code that is SMPTE (Society of Motion Picture and Television Engineers time code, pronounced simp-tee), which “synchronizes the watches” of audio devices. Ever wonder why so many offstage keyboardists and playback engineers use MOTU audio interfaces and Digital Performer software? Because only MOTU hardware can send SMPTE to any analog audio output and receive it on any input, and only DP can listen to SMPTE from any audio input, as opposed to needing a more dedicated kind of sync connection. In the diagrams at right, we show you how it’s done.
Mirrored Rigs: What You Need
· 2 MacBook Pro laptops with as much RAM as possible.
· Digital Performer 5.11 or later installed on each laptop.
· 2 MOTU UltraLite audio interfaces.
· 2 external FireWire drives for audio tracks, 7,200 rpm or faster, with FW800 connectors and, of course, identical DP projects and audio files.
· 1 Radial Engineering SW8 switcher. Connect the audio drives via FW800 and the UltraLites via FW400, and you’ll have no problems with high track counts and multiple outputs