Basically, Ubuntu (-Mate 16.04) plays sound output on the first non-disabled sound-device in the preferences list:
Only trouble: I'd like to change the order. If there's a headset or that USB audio device connected, that should come first, internal card only as the last resort. (Currently I have to disable all higher-up soundcards)
I played around with the
pacmd set-default-sink command (Indices are 0,6,7 on my machine) but no luck...