Adcom GFA-5400 /5500 / 5800 - are they PASS design . Can it be tweaked?

Hi I thought of buying the Adcom GFA -5xxx series amps with Mosfet output as they are available very economical prices considering their Chassis and FETs ( the Schematic looks more like PASS designs except Class AB with higher Voltage power rails. How good are they as a Garage amp ? Also can they be modified for more Class A output.
Welcome ideas and suggestions
kannan
 
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They would be a killer garage amp. Getting kind of dated compared to some of the newer pass designs. Not bad but just not as pleasing sounding as a lot of Pass's other stuff. My take on them is they are detailed, dynamic but have sharp edges to the sound. They do not have the same fitness as the pass labs/first watt stuff. More generic sounding. They are great amps with that being said.

From what I understand, Mr pass designed The GFA 555. After that, Adcom has been tacking on little tweaks here and there throughout their redesigns. So it's kind of a pass design. But not fully.

If you want more of a class A amp, I would probably sell the GFA5xxx to fund a build. Otherwise, there are a bunch of tweaks on the internet for them if you look around. You could try increasing the bias (it is adjustable) lowering the rail voltage with a different transformer etc.