What are the advantages to a Class A amp & what are the trade offs?


I've never had a class a amp but am considering one now. So what am I getting myself into?
128x128artemus_5
It gets hot, eats electricity,less then 40% efficient 
pure class A rarely gets to 100 WPC.
Nobody needs a pure class A amp with 100wpc unless you use it to weld as well. I’ve got a class A 80wpc and it’ll drive any speaker made. It has such a full, lively 3D sound that even non-audiophiles that hear it are amazed. I’m a big fan of class A topology. Don’t think I’ll ever go back to A/B. 
Once I listened to a Class A amp, many years ago, I never wanted to listen to anything else. Some of the older Class A amps used fans which increases your noise floor. The Sumo Gold I ran for a long time used to hit its thermal cutoffs in the summer so you’d lose a channel every once in a while and would have to shut it off until it cooled.

As I mentioned on other threads, I now own a Gryphon Colosseum stereo amp. I think it is one of the most beautiful amps I’ve ever seen and it doesn’t take up a lot of floor space because it is laid out vertically. It has two massive aluminum heat sinks.

What Class A amp are you considering?

There is one maker of a well-regarded tube power amp (I’ll allow he and it to remain anonymous, so as to not appear to be "pushing" them) who offers the amp in both Class-A/B form, and in pure Class-A. Both versions share the same circuit architecture, power supply, tube compliment, etc, differing only in the biasing required to create each version.

The A/B version produces 100w into 4 and 8 ohms, the A version 40w. So why would anyone go with the 40w version? The designer claims (and there’s no reason to doubt him, at least in my mind) the Class-A version produces 1/10th the distortion of the A/B version. How audible is a tenfold decrease in measured distortion? I can’t answer that question.