ProTools 9 Major Phase issue with 192 I/O test

[audiopostpicture]

I don't know if this problem is particular to my system (running 9.03 with a 192 interface on a 2009 Nehalem Mac Pro with OS 10.6.8), but if you're running a slightly different version of software or TDM interface, I'd still like to know the results.

THE PROBLEM:

I discovered some strange phasing and level changes when running a mix through a Dolby encoder, so I ran some tests only to discover that the outputs are out of phase. After troubleshooting I was able to narrow down the pesky phase issue to an apparent software bug.

THE TEST:
I was able to duplicate the issue with these steps:

1. Create a new blank session. I set mine to WAV 48k 24 bit.

2. Create 2 mono audio tracks assigned to two discrete outputs on the 192. Pan them full left and right if needed.

3. Insert a TDM signal generator on both tracks.

4. Sum the outputs to mono (externally) and listen for a level drop. If you mute one track the tone should get quieter, not louder if it's in phase. Or run it through a phase meter if you have one.

5. Once you've confirmed that the signals are out of phase, insert a simple eq (EQ3 one band) after each signal generator. When I do that here the audio pops into phase, and if I subsequently remove the EQ it remains in phase. Saving and reopening, unfortunately does not save the phase fix.

Does anyone else experience this?

[audiopostpicture]

More info:

The out of phase output problem happens with RTAS or TDM signal generators, but it's more severe with TDM.

I tried switching between A and B calibrations, no difference.

I have a HD 2 PCIe card set hooked up to only one 192 I/O interface.

[Rich Breen]

Originally Posted by audiopostpicture

...

2. Create 2 mono audio tracks assigned to two discrete outputs on the 192. Pan them full left and right if needed.

3. Insert a TDM signal generator on both tracks....

Individual instantiations of Signal Generator will not be phase locked to each other. In order to do any meaningful testing of phase you would need to route a *single* instantiation of Signal Generator to multiple tracks by instantiating the SG on an aux, and bussing that to wherever it needs to go.

best,
rich

[audiopostpicture]

Thanks, I'll give that a try and post back.

[audiopostpicture]

As it turns out, I don't have a phase output issue, I have music that was delivered out of phase. Whew, thanks for the signal generator info, goes to show you shouldn't troubleshoot when you haven't slept enough.