This is why 99% of everything out there uses coupling caps.In tube equipment yes, but try to tell designers like Dan Agostino, John Curl, Jeff Rowland etc etc. that. They are firmly in the direct coupled camp, from go to whoa.
I've seen many problems with pieces of even expensive equipment that is capacitor coupled, in that one the cap is not big enough in uF(microfarads), two they use poor quality caps, three sometimes they use electrolytic caps, even I've seen bi-polar electrolytics used.
Still the best cap is no cap.
Cheers George