I have spent some time designing my system and have now almost completed the preamp design. I am at the moment looking into a headphone output, and hence looking at various circuits around the bazaars. I came across a simple circuity using THAT 1646 balanced driver amps that looked promising but I am confused as to why the input is connected to the amp sense terminals rather than pin 4 of the amp. Hoping someone can explain why this has been done. I have attached the circuit here for reference
G'day, have you seen this: https://www.diyaudio.com/community/threads/simple-class-a-headphone-amp-using-that1646.163544/