This is with an AMP2 on an RPI4 with the lastest Buster. The first thing I'll note is that the below command described here didnt work:
amixer sset PCM 90%
Returns: amixer: Unable to find simple control 'PCM',0
I was able to get it working with Digital instead of PCM though. That said, when running alsamixer and setting the volume manually, 50% set from amixer is different than the 50% set in alsamixer. In alsamixer, 50% is -18 db gain, which sounds correct. When set from the cli with amixer though the db gain is -51.50 and the sound is very low. I actually can't hear anything when set to less than 40% with amixer. When set to 100% both are 0 db gain.
Am I doing something wrong or...?