Originally Posted by alan_ct
I have a Adcom GFA555II 2 channel and a GFA2535 3 channel power amp from the 90s. Would a XPA-5 be much better sonicly? Thanks
As fate would have it, I own and use all of the amps you mentioned. The Adcom 555 II is a very nice amp..I bought it in the 90's and never used it much until a few years ago. I've had it hooked to a pair of Magnepan 1.7's and it sounded wonderful. It's currently being used in bridged mode to drive a Magnepan CC3 center channel speaker in the same system as the Magnepan 1.7's. I use a vintage Threshold S500e to drive the 1.7's now. The Adcom GFA2535, which is a 4 channel or three channel configurable amp , sounds very nice as well, but doesn't have anywhere near the power of the XPA-5. It's rated at 4 x's 60 watts per channel in 4 channel mode OR 2 x's 60watts per channel and 1 x's 200watts per channel in three channel mode. (all at 8 ohm load). In non bridged mode, it is rated at 90 watts per channel times 4 at 4 ohms.
That 200 watt bridged channel has limitations. For example, I tried using it to drive that Magnepan CC3 center channel speaker and it didn't like that load one bit. It would overheat and sound strained. The bridged Adcom 555II sounds far better and runs cool. I am using that 2535 now, at least two channels of it, to drive my rear speakers in that system..a pair of Magnepam MMG's. It works just fine in that application. In non bridged mode, the 2535 has no problem handling 4 ohm loads.
I use my XPA-5 in my main system built around Thiel 3.6's, to drive the surround channels in a 7.2 configuration. It's a very powerful amp and sounds great. I don't think it sounds any better than the Adcom 555II though, they are both fine quality pieces of gear. Within it's power limitations, the Adcom 2535 is a fine sounding amplifier..HOWEVER...it is a 60 watt per channel amp at it's core. Bridging one of the sides to gain a 200 watt rating into a single channel works as long as the speaker you are driving is 8 ohms. If it's less than that, that bridged channel will have issues. Even within that limitation, I don't think that bridged 2535 channel could be considered the equal of a channel of the XPA-5.