Adcom 555 Mk 2 Questions

Has anyone run these amps in mono mode? How did they sound?

I have a old 555 and I think it is a MkII because the RCA inputs are wide apart, not right next to each other as I see the originals are.
It has excellent sound. Not bright at all like some of the folks above speak of. I have it taking signals from a Dynaco Pass and feeding Acoustat 2s. This is great symmetry. The warmish Pas preamp and the big SS Adcom make beautiful music together.
I am interested in modding to some degree. First up will be cutting a hole in the chassis and installing a IEC plug socket. Afterwards the input board caps.
I don't see much to do to the power supply,since it is quite huge. This thing looks like a big empty box with one smallish board, a big toroidal and 4 big power caps.
Any mod info would be helpful.

e

I used an adaptation from an old Audio Amateur article to build a fully regulated power supply and it made a big difference in the sound quality especially with dynamic swings.

Kal

Hi, I know this thread has been going on for ages now. My opinion for the GFA-555 is a powerful and very quiet amplifier. Those who say it gets hot ,well there must be something wrong w/ it because mine does not even get warm under a heavy load. For the price used mine was $300 from Audio Classics sight and sound unseen just on reputation (SHIPPING THROWN IN ) and it came slippery clean and work the 2nd I hooked it up. I know tubes take time and I don't have the patience or that so I went ss and it's really instant on and does not get better the more you play.Yes when you shut it own and it spools down i does take a few minutes but who cares, your done listening. I sometimes leave the amp on all the time and I'm torn about this because most the people over on the POLK site swear by it and I must be a hypocric because  I have a sub woofer that has never been off since I got it about 9 y/o. For durability, price point ,looks, and form and function one could not  do much better.  For a starter amp or even your go to amp I would not hestate and go for it. My model is a bit different ,I have the rack face model used for recording studios because of their power and low noise floor. Highly recommended  for a step into 2 chll genre....Some say it's a bright sounding amp. I have no way o comparare and would like a Parasound or Bryston to get and hear the difference....Lew

Your adcom is too hot, hiss as well, it is sick and needs a doctor! My adcom gets a bit warm driving 8 ohm b&w dm4 spkrs at loud volumes and no hiss whatsoever.