I have an Axe I/O solo and the headphones work fine and a set of reference monitors on L1/2 out and they work fine too but they don't mute with the headphones plugged in. The monitor is to see how the room effects feel in a real room after composing on the headphones to allow the set up to be rolled up without upsetting the neighbours. Is this the intended operation ?
I can just turn them off but that makes it a little awkward to use. I unlocked the Triple Crown on Max and that amp sounds best when slightly over driven at 4+ which the neighbours don't appreciate for some reason.