Changing outputs during playback causes digital noise on input channels

[krocksf]

I'm seeing a strange issue on my M1 MacBook Air running Pro Tools 2022.07 on macOS 12.4 (Monterey). I use an external summing mixer in my set up...and I've see this happen with both an Apollo x16 and an Apogee Symphony MKII 32x32. I create an Aux track with input channels 3 and 4 assigned to the interface so that I can monitor the mix coming back into Pro Tools. I then started playback and while playback was happening I assigned one of the audio tracks out channels 1 and 2 of the interface into my mixer. I did this a couple more times on a couple other tracks and eventually I got some nasty noise coming into the Aux track that was taking the input from interface channels 3 and 4. It's like a digital noise (like a super small buffer repeating super fast).

The noise persists, even when playback is stopped. You can switch the input of the Aux track to channels 1 and 2 and the problem will go away, however as soon as you switch back to channels 3 and 4, it will come back. The only way to get it to stop is to either relaunch Pro Tools or toggle the sample rate on the interface to something else, and then back to what it was previously set to (in my case from 44.1 to 48 and then back to 44.1).

And weirdly enough, I've only seen this happen on inputs 3 and 4 at the moment. I haven't gotten it to happen if I start with input channel 1 and 2.

The noise is pretty nasty, so it's pretty annoying when it happens, and definitely interrupts your workflow. Anyone else seeing this?

[peapodpost]

maybe something(s) are having a hard time switching sample rates when you don't want them to?

can you hard-assign the same sample rate to all your gear?

use a buffer audio driver such as loopback, blackhole, omnibus, etc?

[Darryl Ramm]

Originally Posted by peapodpost

maybe something(s) are having a hard time switching sample rates when you don't want them to?

??? Nothing here will be switching sample rates, it's the same interface, it runs at one sample rate. (until manually changes to solve this problem).

[krocksf]

Exactly. My interface is set to 44.1, which is what the session is set to as well. All input/output changes are made in the same sample rate. When this problem occurs, I have to go behind Pro Tool's back to toggle the sample rate to fix the issue (using either Apollo Console or Apogee Symphony Control). Pro Tools will post a dialog about there being a sample mismatch, but after you dismiss that, things are back to normal.

[krocksf]

Sorry, and to be clear...I'm using a single interface...either the Apollo x16 OR the Apogee Symphony. This happens when I'm using these one at a time as my playback engine.

[Eric Lambert]

Do you ever experience this issue when switching with playback stopped?

I can't say that this is a new one, though I've come across it so rarely that I've never figured out exactly what caused it. I'm guessing I would have increased the buffer size, which tends to give PT more breathing room to handle tasks like this, and I'm guessing that it worked because I can't recall any further troubleshooting afterward.

[MarshallV]

I’m having this EXACT same issue! I’m getting playback from output 3/4 whether I want to or not. High pitched squealing noise from Pro Tools and Symphony IO. Something truly bizarre is happening. I like to analog sum my mixes so this kind of behavior from PT can’t be a thing for much long 😭