I picked up a NUX MG-300 guitar effects unit with high hopes that it would work under Linux, since it is supposed to be a class-compliant USB audio device.
Unfortunately, it did not work out of the box. After some back and forth with the maintainer of the Linux kernel sound subsystem, we managed to get audio capture working, but never managed to get playback working. Everything seems to be operating correctly, but the device produces no audio output over USB.
I have admitted defeat and will be returning the device.
The discussion on the alsa-devel mailing list can be found here:
https://mailman.alsa-project.org/pipermail/alsa-devel/2021-January/179348.html
It at least resulted in a kernel patch to enable audio capture.
I also had no success getting it to work with Android - even with some of the apps that have their own custom USB audio implementation.
If anyone has more luck with this interface down the road, please let me know.
Update: As a last ditch effort, I gave the interface a try with the aforementioned kernel patch on my Raspberry Pi 4, which was running about a year old kernel version. And it worked. Sort of. It initially worked perfectly, but I found after more testing that it is sporadic. Sometimes it worked fine, sometimes only playback worked, and sometimes only capture worked. Not sure what needs to be done to get the interface working reliably.
