Originally Posted by ozshadow
I didn't see any decoupling caps. Do the buffers act in a similar manner to remove DC offset ? I am curious about whether I need to add caps in the signal path of my Alien DAC.
I think you are confusing some terms here. I suspect you mean coupling caps, which are used to remove DC from the signal, and there are none of these, or any other method of removing DC offset in this amplifier. The buffers certainly dont help lower DC offset, and in fact, it is only the fact that they are being run closed loop that prevents them from exhibiting a small offset of their own. That said, you dont need to add coupling caps to your Alien DAC, but you must do something to block the DC it puts out, or fry your headphones, which is most easily solved by coupling caps, though could also be solved by playing games with a virtual ground on the DAC floating midway between ground and supply, equal to the voltage of the offset. This cant be implimented on the existing Alien DAC pcb, so you would have to either hack the board, do it offboard, or design a new pcb with that in mind. Or just add a pair of coupling caps, and dont worry too much about it.