UAC-8 in class compliant mode on Linux (UbuntuStudio 24.04) works fine but Ardour crashes. When I set the buffer to 2048 or more, start Ardour and only then turn on the sound card, it doesn’t crash. Otherwise, without Ardour I can work on other programs with a much smaller buffer. I assume this is because the card works on the USB 3.0 interface. Does anyone have any advice?
ALSA backend? Or Pipewire/JACK backend?
Do you then stop the ardour backend and reselect the newly available device? It feels like you must be leaving out some steps, since Ardour obviously cannot use a device which is not yet present, and Ardour will not change the selected audio device unless you manually force the change.
Are you seeing any USB subsystem errors in the kernel message log that leads you to believe that? Have there been other reports that connecting a UAC-8 to a USB 2 controller has different behavior than connecting to a USB 3 controller?
What leads you to assume that USB 3 is involved in the problem?
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I tried all the options for several days. Alsa, pipewire, UAC-8 multichannel, UAC-8 Pro audio… I even used a USB 2.0 cable. The only thing that helps is to turn off the power to the sound card and turn it on again while Ardour is running. After that, I adjust the inputs and outputs and of course, I put a big buffer in the audio settings. Currently 2048. On the old laptop, the buffer is at 4096 to prevent it from crashing. Such problems with a large buffer only appear on Ardour. xrun appears on the smaller buffer and soon there are several hundred of them and then it crashes. Audacity works without problems. focusrite 18i8 usb 2.0 has no problems, even on a very old computer. I use that in rehearsal. Thanks
Looks like I found a solution. I connect UAC-8 with a USB 2.0 cable and I connect UAC-2 with a USB3.0 cable. I use UAC-8 for input, UAC-2 for output. Buffer at 256 and everything works. No Xrun, no crashes.