I am having the same problem with the USB audio output from my Mac Mini, but to a PS Audio DAC.
All was working OK, but the Mac mini crashed last week and I can no longer connect from Roon to the DAC using USB.
The mac is up and running again and as far as I can see all the settings are the same as before, and the PS Audio USB shows up as the default USB output in the Mac Audio settings.
However as soon as I try and play a track in Roon the audio output switches to HDMI (or the Mac built in output), so no signal is getting to the DAC. If I pause the playback … the audio output selection returns to the PS Audio USB !!!
I am going insane trying to solve this, so any advise would be much appreciated.
When playing to the DAC in “Exclusive Mode” Roon will prevent other audio applications from playing to the device. When macOS detects this, it automatically switches the audio output to a different device so that things like system sounds and other applications on the Mac will have an audio output to route themselves to.
This doesn’t explain why you are not hearing audio from your DAC when you attempt playback to it in Roon.
Ensure that you have enabled the PS Audio DAC in the Settings > Audio screen in Roon and that you have selected the PS Audio DAC zone for playback in Roon. Avoid using the “System Output” zone as this will route the audio through the system mixer.
I’ve included the Roon Knowledgebase link about zone selection below:
Just before I got your reply I thought I would have another try, so I tried playing iTunes through the USB output to the DAC which worked OK.
… then switched to Roon … and now its working OK !!
I haven’t changed any settings but it all seems to be working now (fingers crossed). I must admit it’s a bit of a puzzle and has been very frustrating. Perhaps it was something to do with the PS Audio DAC that was causing the problem and has now reset itself?
Glad to hear you’re back up and running. The large majority of Roon customers are greeted with a Plug n’ Play experience, but occasionally issues pop up and that’s what we’re here for. Feel free to open a new thread if you run into any other bumps in the road, we’re happy to assist!