Support for NUX MG-300 USB interface

[Takashi Iwai]

On Tue, 19 Jan 2021 18:40:04 +0100,
Mike Oliphant wrote:
> 
> Your mixer.c patch does get rid of the RANGE errors. No change to behavior,
> though.
> 
> I'd already tried setting "implicit_fb=1" even though I didn't expect it to
> work, since there is a separate feedback endpoint. I just tried it again - it
> doesn't seem to hurt anything, but it doesn't help either.
> 
> Capture seems to be working perfectly with the clock patch - I'm not sure why
> I was initially getting noisy input.
> 
> I checked "/proc/asound/card*/pcm*/sub*/status" during playback, and the
> pointer seems to be moving forward as it should. All indications are that the
> system thinks playback is working fine.
> 
> One interesting piece of information - alsamixer shows two stereo outputs
> ("pcm" and "pcm1"). Not sure why there are two - maybe output is going to the
> wrong one?

You might need to unmute and increase both.  The first one should be a
master volume/switch while the second one is for the stereo channels.

Naming the mixer elements properly for USB-audio is a really tough
task.  Many firmware don't set the right strings and a guess work
doesn't fit to all.  But certainly there are some rooms for
improvements there.


Takashi