Hi there! First thanx for making my life easier, just entered the world of Balena 
Anyway: I’m using RPi 2/3 with external USB soundcard (SoundBlaster Play!).
Everything works well, Balena volume is at 75% (can be changed, ok), but the default volume of the soundcard is set to (I guess) 26 and audio is very quiet. I can set USD soundcard volume via alsamixer to 100, but it’s not persistent, after reboot it’s set again to 26. Plz, any clue how to make the volume persistant? Thanx a lot!
Hi and welcome to the forums @maxim o/
did you by chance set the AUDIO_OUTPUT env var?
see https://sound.balenalabs.io/docs/customization/#general