ADAT Out stops sending audio during show

[dwood3455]

Here is the setup. Macbook Pro with SSD and 8Gb ram running latest version of Qlab and OS 10.9.2. Updated MOTU drivers. Firewire 800 into two daisy chained 828mkiii hybrids. ADAT out of 828's into M7CL console. Using the first 6 channels of ADAT for a dance show. Once last night and once this afternoon the sound abruptly and unexpectedly cut out. Qlab was still running and the meters on the 828 were still bouncing. This is after hours and hours of tech rehearsals so I doubt a bad cable. I plugged headphones into the 828 and all sounded fine. Both the 828's and the console are clocked by a Big Ben and everything looked fine there. The MOTU just stopped sending digital audio out of the ADAT ports. My work around for the show tonight is to run Analog out to the board but that kind of kills all my discrete digital routing. (On a side note I constantly multitrack 32 channels out of the M7CL into the 828's and have never had a problem.) Anybody have any ideas or suggestions. Thanks in advance.

[HCMarkus]

A random thought:
Are you using a UPS for the audio gear AC (excepting power amps, of course)? I'm thinking voltage drop when everything is happening during your show...

[dwood3455]

I am using a UPS, but have never experienced a voltage drop. If the UPS kicks in though there is an audible chirp alerting you of the problem and I haven't experienced any of that. It is all clean power coming from a dedicated 200A panel. Do you think a voltage drop would cause ADAT out to cut but keep everything else running fine? Thanks for your reply.

[HCMarkus]

I am using a UPS, but have never experienced a voltage drop. If the UPS kicks in though there is an audible chirp alerting you of the problem and I haven't experienced any of that. It is all clean power coming from a dedicated 200A panel. Do you think a voltage drop would cause ADAT out to cut but keep everything else running fine? Thanks for your reply.

Just a thought. Random.

[TinenTech]

I vaguely remember something about ADAT Optical chips that involves them reclocking on their own…I was running into a Yamaha 02R and it did something similar. The ADAT was still sending, it was the Yamaha that automatically muted because of a clock mistiming. (There may be a parameter in the Yamaha that you can change so it doesn't mute, but allows a "click" if necessary?)

Instead of connecting the Big Ben to the Yamaha's Word Clock In, connect it only to the 828 and clock the M7CL to the ADAT IN. It's "wrong" (or at least, not the normal way of doing it), but it might avoid some obscure problem.

If you have the problem again, try immediately plugging the ADAT Optical into some other hardware (like an old ADAT or an AI-3) you can listen to, to verify that the 828 isn't sending optical out.

[dwood3455]

Thanks for the reply TinenTech. I have not had the opportunity to replicate the exact situation since my original post. I will definitely try your suggestion when I have the chance. It was recommended by MOTU to clock the console and the two 828's from the BigBen word clock and I hadn't had any problems for over a year until this post.