Downgrading macOS from Tahoe to Sequoia: User accounts, Time Machine, firmware

Thank you, but as I've already stated in this overlong thread, the problem occurs even if the headphones are connected directly to a USB port on the Mac. This was not apparent on my first try, but on repeated investigation it has become clear. The presence of the hub *appears* to be a factor in that it affects the time to onset, but it is not critical.

Thank you, but this part of my question has been answered already by several posters. I am not currently contemplating the downgrade - treating it as the "nuclear option" for now. It may come to that if there is no fix from Apple for the underlying problem*, as I really need to use headphones for my work because of my living situation. But for now I plan to work with the company as far as I can.

*If anyone doubts that there is an underlying problem in the OS, please see the other thread I linked to below last night, and those linked to from that thread. At least one other poster has reported a seemingly identical problem: gradual audio degradation that begins soon after audio starts playing, and that only occurs if the audio device is USB headphones. I have asked Apple to add that link to my case, since the last senior advisor I spoke with said that he had never heard of a similar issue.

Of course there's always the possibility that installed software is a factor in whether the issue is tickled - but even if so, I'm not sure one could implicate that software as "the cause". The gradual degradation of audio and the fact that killing coreaudiod temporarily relieves the symptom both point to a problem with coreaudiod's ability to control the audio hardware, perhaps due to a memory management problem or even running out of memory due to system load - though I suspect not, since it happens even in safe mode with only Apple Music running.

I do not have Bluetooth headphones or any way to connect these headphones via the headphones jack, nor do I know of a way to connect them using Bluetooth. They are USB-A and thus require a dongle (I have Apple's USB-A to USB-C adapter) - now that I know that the distortion occurs without the hub in the data stream, I've even considered that the dongle may be the critical factor. But I have no other way to connect the headphones.

Later today I will try to stream the coreaudiod logs while tickling the issue and see if I get the same results as the other poster. That is the only test I have not yet tried, but it seems that for at least the other poster, the logs point clearly to coreaudiod or something that affects its performance.

I streamed the audio logs using the shell command from the other thread and can confirm two of the three error messages that user reported: I see usbaudiod: [<private>] current microframe timestamp calcError repeatedly, and coreaudiod: (libAudioIssueDetector.dylib) [com.apple.coreaudio:aid] occasionally - on one short run using Dorico Pro (music notation software) in which the audio began to degrade almost immediately, it occurred exactly once, though numerous instances of the other error were logged in that short time.

I do NOT see the overload errors that the other poster saw. And the usbaudiod timestamp calcError messages are frequent and occur independently of whether there is noticeable distortion. The libAudioIssueDetector.dylib message from coreaudiod, on the other hand, I have so far only seen when the audio has begun to degrade. It is not emitted frequently, but it appears to be emitted, consistently, at least once after the distortion has begun to occur.

Just some additional info, for anyone who is following this thread, and to point Apple to if needed later on.

Best Buy ran a full hardware diagnostics suite on my Mac, including the Audio Test. Everything came back a clean pass, confirming that this is unlikely to be an issue with my hardware. Now, the question is, will Apple connect the dots and follow through on this to come up with a fix for whatever the underlying issue is?

While I was there I picked up a cheap pair of Bluetooth headphones, mainly to try. As expected, there is no evidence of the audio degradation (at least so far), so in a sense I'm no longer crippled by the bug. But it's not my way just to drop a case when it's clear that without help from their users, Apple is unlikely to either have or be willing to devote the bandwidth to find the root cause. I'm willing to work with them for as long as it takes - at least for the duration of the summer, until the academic year starts up again end of August.

Yes, that's what I've always understood. Thank you.

I don't think @weeklycod meant to install Sequoia OVER Tahoe and didn't take it that way. I am not sure why people are raising this point. Obviously the internal drive must be wiped.