CLASS A AMPLIFIERS

What caught my eye in the Stereophile measurements was paragraph 3 where they state it's a 935 watt amp continuous, almost 30db. It doesn't put out 1870 wpc into 4 ohm or 3740 into 2 ohms continuous. "However at it's rated power of 600 wpc, which is 28 db, it would hold that rating for all loads from 8 to 2 ohms". I read about many an amp that put out 100 into 8 and 150 into 4. What if that manufacturer decided to rate it at 75 into 8, even though it put out 100? Then he could say it "doubled down" to 150 into 4. Impressive little amp then. Nobody is going to sue anybody if they buy a 75 or 600 watt amp and it puts out 100 or 935 respectively. Gee, I got more than I paid for. But it's the wordage I look at. Doubles its "rated" power is honest but to me, it is what it is, and if its "really" a say 250 watt guy, I'd be curious how close it came to 500 into 4 but most important is how it sounds into 4 or 2 ohms. Some amps start to get a little unhappy down there. If it makes someone happy to believe their amp doubles down that's fine but I don't listen to specs so my criteria is just "does it draw me in".

Onemug, may have a point. Bear with me for a moment and forget the "most speakers are damaged due to being under powered rather than to being over powered". What if a speaker manufacturer refused to honor a waranty because one used amplifiaction that was rated within the speaker manufacturers standard 8 Ohm limits but actually exceeded its 8 Ohm rating?

Onemug

I agree with you that in the end its the music not specifications or circuit toplogy that we listen to. And one must keep ones eye on the ball when reading and comparing specifications when trying to make a purcahse decision. But it does lead to some interesting conversations and I really enjoy the learning that goes along with it.

Chuck

Interesting reading, and discussion men. Thank you. Now I know why I love my FPB400cx! The "real" Krells do sound wonderful on every type of music in my system. :-)

Unsound, just so you know, Class A has nothing to do with push-pull vs single-ended. Also, a Class A amplifier's peak power will always be the same as its continuous power, IOW the 'headroom' rating will be 0db. An amp that has more that 0db headroom is likely an AB amp.

Krell's sliding class A approach (a similar form of that being first used by Brooks in the 50s if I recall right), allows the amp to run cool at low power. On account of its power supply regulation it should exhibit 0db headroom.

Changing the load impedance changes everything! Contary to popular belief it is not always a good thing that the amplifier power changes as the load impedance changes. There are speakers that are of course designed for this, and there are other speakers to which this behaviour is unacceptable (i.e. electrostatics, horns and full-range high efficinecy drivers to name a few).

This ability of transistor amplifiers has to do with feedback just as much as the fact that they are solid state. The effects of Negative Feedback in an amplifier runs counter to the way our ears have evolved over millions of years. As a result it is one of those things that we should always question. Once you do so *honestly*, a lot of other things get questioned too, but ultimately the right answers also yield better sound. BTW these comments have nothing to do with transistor vs tubes! -although many will think that they do. The underpinning issue is more fundamental.