But the MOTU 16A doesn’t exhibit this at all. When its captured playback is played against the original test file, or played against another test pass, it syncs perfectly. Almost nulls without any drift. I ran 5 passes through the 16A, and it still (nearly) nulls without any phasing.

I know clock syncing is critical when using two interfaces at the same time in the same project…but since my test file wasn’t recorded on either system, I thought I’d hear the same type of imperfections (noise, frequency response discrepancies) from both DACs. And I was surprised when one was so phase/drifty. You know what I mean? Maybe I’m wrong about that.