Thanks Mervinb. The specifics of what you said elude me but I take on board the general idea . Here is some info on the Moon hdam: OPA - Moon : This discrete opamp uses dual differential gain stage and single ended output stage circuit design , we try and audition for a long period of time . The OPA-Moon sound characteristics is a bit of tube-like (vacuum valve) , soft and slightly thick, and full of emotions . THD Less than 0.0008%(1KHz), Operating voltage ：±9 TO ±25V，Open loop gain：33DB，Operating current：Approx. 28MA（Single OPA） ， Approx 58MA（Dual OPA）. I have a dual which was needed to replace the Burr Brown 2604 opamp in my Zero Dac.