FYI they are looking into it. I've been having a back and forth with Apple since the 9th. In my case they escalated it to
Engineering/T2 Engineer after a couple phone calls. Engineering requested a system diagnostic two days later and I've been sending them everything I can since...
I can also tell you exactly what kicked it off for me...
Security Updates 2018-002 and
2018-003.
The 1st 3 months my machine had no distortion, audio playback was clean. After installing both updates the issue appeared 15-20 mins after restart. Since it's a security patch there was probably some T2 software in the updates, and since the T2 handles audio it's another strong indicator that the T2 probably plays a big role.
If a patch broke audio, the issue can and will be patched. The fastest way to get it patched is for
anyone experiencing the issue to call and have them escalate your case. If you have to, keep calling until someone escalates the issue to engineering. The more diagnostics and scenarios they collect the sooner a patch will happen.
The main thing for me is holding the line and not letting them force upgrade me to 10.14, (project/compatibility reasons...) My hunch is it's a band aid that doesn't fix the underlying issue, sure seems like it from the thread...
Anyway, here's what I've noticed so far...
- Distortion happens in headphones as well as speakers.
- Quitting all apps using audio or streaming makes it go away for a short period, it comes back after a few hours. (Assuming some kind of system timer is part of the issue.)
- Logic's reports incorrect sample rates when the problem starts. "Error while trying to synchronize Audio and MIDI Sample Rate 40,875 Recognized. Check conflict between Logic Pro X and external device."
- I don't use an external interface with this machine. Something else is setting an incorrect Sample Rate.
- The distortion sounds exactly like jitter. (Logic recognized sample rates 41,158, 41,151, and 40,875. It is jitter.)
- The more audio streams the worse distortion gets, (another clue it's jitter.) I.e. if I launch iTunes with Logic open the distortion turns from crackling to a pulsing distortion. Sound begins to stutter and "echo". Basically something's getting caught in a buffer somewhere, once more then one source is streaming audio.
- The distortion occurs in all DAWs. No better or worse in any of them... Audio buffer size seems to have no effect.
- The distortion occurs in iTunes with nothing else running. Same with Chrome. If I Chrome is streaming video and I launch iTunes the distortion starts pulsing at regular intervals, like Logic w/ iTunes. Same effect, sounds get caught in a buffer.
- I timed the distortion using only iTunes and it happens every 10 seconds so it's cyclic. (At least on my machine...) I took spectrograms and you can see how consistent it is.
Anyway two days after they escalated it to engineering, engineering requested a system-wide diagnostic from my machine. Since then I've been sending them everything I can... Screenshots of Logic Sample Rate errors, screen recordings where I leave console open and let the issue appear, then pasting the console reports to text with notes and timestamps, quitting and launching apps to try and force the behavior...
Couple screenshots...
Happening in intervals...
Looks like jitter to me...
