PLEASE HELP! SPDIF return problem

[branagan]

Good Afternoon everyone. I have a huge problem and I hope you guys can help =]

Setup: G4 MAC with DIGI002 Rack, Mackie Digital 8 Bus (D8B) board, Protools 7.0 / 7.3.1 (I tried my issue with both versions and various service packs)

My problem arises with SPDIF. I have Protools run back to the board and I do my mix on the board. Then, I make up a new stereo channel that records that mix. I route the input to the channel as SPDIF return from the Mackie board and I route the output to a dummy output channel (so that it’s not causing a feedback effect). I also mute the channel just incase. I then hit record enable and then hit play like normal tracking.

THEN THE PROBLEM ARRISES: I go to play back the return track I just made and on the LEFT channel there is popping like crazy! Little digital-looking spikes appear above and below the 0 line. You also hear it. While it was tracking, the meter on Protools on the left channel was also spiking all the way up.

At that point... I whipped out my mbox2 and ran the SPDIF to that instead of running it back to the same Protools rig. It worked just fine when recording to the MBox on a separate Mac. I feel like there is something simple that I am missing to fix this issue.

Any ideas?
Responses are greatly appreciated.

[Slim Shady]

Sounds like a clocking problem - you need to set up the master/slave relationship as far as the digital clocks go on your two devices. Either PT is the master and the Mackie clocks from it, or vise-versa.

[branagan]

Slim… thanks for your response =)
Clocking is somewhat new territory for me. Is clocking involved with the midi cables running back and forth between the Mackie and PT? I have been trying to get the Jog & Shuttle to work to use the Mackie to control Protools... But I have been unsuccessful so far. I have recently found some new documentation from the Mackie site on how to do it with a similar-model board, but I have not had an opportunity to try it out yet.

[Slim Shady]

No, clocking has to do with your S/PDIF connections. One device needs to be the master clock, the other device needs to slave to the master. In PT you set this up Setup->Hardware - and by default internal clock is the master. Can't help you with how to set it up on the Mackie, but it's going to be clocking internally as well by default, so right now you have two devices that are both trying to be the master clock, which doesn't work.

[branagan]

Oh ok! Thank you so much again. I will try this tonight! Does it matter that I only had 1 SPDIF cable running instead of 2 to make the complete loop?

[Paul Maunder]

No, the clocking information can be carried on just the one cable. If you're not sure how to set the Mackie to slave off pro tools, just try opening the session setup window in pro tools and changing the clock source to s/pdif. That way, pro tools will be clocking off the Mackie and shouldn't cause clicks & pops in the audio.

[branagan]

Paul and Slim... Thank you so much. This your advice has solved my problem!

I set Protools to be the slave in the hardware dialog box (apparently I cant put the Mackie into slave mode... or i just cant find it in the manual yet :-[ ... no big deal.) The popping went away.

Thanks again!!