Are you going with a 4 wire system for the headphones? I played around with current feedback before a forehead slap moment, realising that I'd have to mod the headphones to change the common ground to stereo. Going open loop + DC servo for now.
Thanks. You just gave me quite an interesting academic exercise to think about, both as an op-amp version and as a discrete version. Maybe for a future project.
Just the question of open drain vs common drain can lead to many different topology ideas with no clear 'winner' known ahead of time.