HD I/O - ch 1&2 out of phase with ch. 3-14

[guitarman6]

While calibrating a system yesterday and running a 1k tone through all 16 channels of an HD I/O I discovered ch A1 & A2 are slightly out of phase with the other 14 channels. See attached images for reference.

We ran the same test tone through all 16 channels. Patched the output of each channel directly into the same channel's input and recorded signal to check for phase coherency.

Is there some internal mix buss voodoo with Pro Tools and Ch 1-2 since those are usually reserved for master bus / monitoring?

Is there any other reason that would explain why the first two channels are out of phase with the remaining fourteen?

System Specs: MacBook Pro M1 running PT Ultimate v23.12.138 via HDX card in Sonnet Echo III Thunderbolt Chasis connected to AVID HD I/O with 16 analog ins/outs. Test session was using AVID's own "HD IO Calibration Session (16 ch).


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[tope d]

Originally Posted by guitarman6

While calibrating a system yesterday and running a 1k tone through all 16 channels of an HD I/O I discovered ch A1 & A2 are slightly out of phase with the other 14 channels. See attached images for reference.

We ran the same test tone through all 16 channels. Patched the output of each channel directly into the same channel's input and recorded signal to check for phase coherency.

Is there some internal mix buss voodoo with Pro Tools and Ch 1-2 since those are usually reserved for master bus / monitoring?

Is there any other reason that would explain why the first two channels are out of phase with the remaining fourteen?

System Specs: MacBook Pro M1 running PT Ultimate v23.12.138 via HDX card in Sonnet Echo III Thunderbolt Chasis connected to AVID HD I/O with 16 analog ins/outs. Test session was using AVID's own "HD IO Calibration Session (16 ch).


If image does not appear you can also view here.


If image does not appear you can also view here.

Hi There!

I saw your support case and I've bumped it up the team. Thanks!
(Case 04763809)

[XJENSEN]

Dear God. Gremlins. Following.

[BScout]

Originally Posted by guitarman6

Patched the output of each channel directly into the same channel's input and recorded signal to check for phase coherency.

Send 1-2 out to 3-4 in and send 3-4 out to 1-2 in. See which channels are delayed then (on return)

[martthie_08]

do you happen to have master outs for 1-2 and not for the others in your session?

are you using a printed sine wave or the "signal generator" plugin?
I would strongly recommend to use the latter in case you are using a plugin.

[Rich Breen]

While it's not impossible that this is a bug, I'm curious if there's a patch bay involved with half-normals and there's any loading on 1 and 2 that's not on the rest of the outputs, or were the outs and ins completely lifted from anything else in the outside world when patching out to in?