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Q. How do I ensure the show goes on when a live backing track fails?

By Hugh Robjohns

I’m about to take on the task of running live backing tracks for Hacienda Classical live shows, and although I already use Pro Tools for backing tracks (for Peter Hook and the Light) this system doesn’t have a backup facility, or at least not one that runs alongside in sync. I want to run backing tracks on two systems, synchronised to each other. However, if one systems fails, I want the second system to keep running regardless of lost sync — is this possible? I would also need it to automatically switch the DI outputs to the second system.

Andrew Poole, via email

SOS Technical Editor Hugh Robjohns replies: Yes, this is certainly possible! The synchronised backup is easily achieved by using a reference master timecode signal. That can either be provided by the master system, or from an external master timecode generator, depending on what kind of system security and control you require. The master and slave systems can be hardware machines or DAWs — or even a combination of both — and you simply need to configure the slave system(s) to continue running should the master timecode disappear, which is a pretty standard timecode-chase option. You’ll also need to configure how the slave machine(s) should behave if the master timecode comes back (ignoring it is probably the safest option). Remember that if you’re using digital systems you’ll also need to make sure they are synchronised to the same independent word-clock master (timecode is a positional reference, not a clocking reference).

The ‘DI box with automatic switchover’ function is quite a specialised requirement, but there are at least two companies I know of that make suitable units. In most cases, the switchover is triggered by the loss of a continuous tone signal replayed from the master machine and routed to the switch box via a spare channel. Check out the offerings of Radial Engineering (www.radialeng.com/sw8.php), who have both four- and eight-channel switching DI units, or Orchid Electronics (www.orchid-electronics.co.uk/Switching_DI.htm), who make an eight-channel version. Multiple units can be linked together for higher channel counts in both cases.

Published February 2016