Anyway, I want to start swapping op-amps. I am using this with HD650's. Anyone know of a few posts I can reference that comment on the general consensus of rolling which op-amps produce accentuates what sounds? I'd like to warm up the mids a little and tighten up the bass if possible, without buying a tube amp.
Many tube amps create a warmer sound.
It's highly unlikely one will tighten up the bass on the HD 650. That's not the way tubes, amps, and headphones work.