I've been using a Schiit Modi 3 D/A converter for my main desktop audio for a year or two. In the last week, it's been sporadically vanishing from PulseAudio.
It's normally plugged into a USB port on my monitor, which has several such ports, all of which work with other devices. When I plug it in, dmesg shows me:
[2126764.183346] usb 3-3.4: new full-speed USB device number 75 using xhci_hcd
[2126765.035388] usb 3-3-port4: Cannot enable. Maybe the USB cable is bad?
[2126765.887389] usb 3-3-port4: Cannot enable. Maybe the USB cable is bad?
[2126765.887461] usb 3-3-port4: attempt power cycle
[2126768.319399] usb 3-3-port4: Cannot enable. Maybe the USB cable is bad?
[2126769.171424] usb 3-3-port4: Cannot enable. Maybe the USB cable is bad?
[2126769.171483] usb 3-3-port4: unable to enumerate USB device
I get similar messages from other ports; other devices show up fine. This port is successfully providing power to the Schiit.
Though "Maybe the USB cable is bad?" is a dubious-sounding message, I did swap out the existing random cable with a brand-new good-quality one, with no difference.
I also tried to plug the Schiit into a Debian laptop, with the same results as above. Confoundingly, after this test, I re-plugged it into my monitor and it magically started to work -- it showed up in dmesg, it started to play audio.
However, hoping it magically works isn't a good long-term solution. Is there any way to figure out what's causing this? Could it be a hardware problem with the Schiit? If so, how do I report it to them?