Why are most High End Amps class A

I am so much at awe with what true Class A amplifiers can do to my life that I just want people to check them out.

Spatine, I really don't disagree with you in any fundamental way - it's just that for me, I could say this about a number of different classifications of audio equipment, not just Class A amplifiers. And I do indeed value a rational, disciplined approach to the craft of designing and building audio equipment over a dogmatic approach . . . mainly because I consistently have positive musical experiences from systems that don't fit into any particular belief system.

A well-executed Class A amp can indeed show the true potential of solid-state amplification . . . I simply feel that it's possible these days for Class B amplification to be just as good (and better in some ways) if properly applied. It's just unfortunate that the market is brimming with too many examples to the contrary.

Kirkus - we're not talking about absolutely best amp in existence but about one that is about 100W/ch and less than $3k. Do you feel that class AB amps would have certain advantage here over class A (less estate = better components)?

Kijanki, let's look at it like this . . . and this is kinda what I was getting at when I talked about an amplifier being "well suited to the application".

A realistic amount of juice necessary to drive most of the domestic audiophile loudspeakers to comfortably high domestic volumes is, say 25 volts RMS . . . (approx. 75W/8 ohms or 150W/4 Ohms). I feel that a high-quality amplifier must have a low output impedance in order to have predictable performance into the types of loudspeakers that are likely to get connected to it. If we then to honestly call it a "true Class A" amplifier, it must maintain class A operation to the lowest realistic impedance that the amplifier will see -- let's say 3 ohms.

Our class A amplifier will then operate from 20 volt rails, have a quescient current through the output stage of 13.5 amps, and thus dissipate at least 1100 watts of heat for two channels (you did want stereo, no?). If we want this amplifier to be reliable, consistent, and last many years (because it's hard to enjoy the amazing sound quality of a broken amplifier), we need to keep temperature rise to a minimum (do we include the gentleman who lives in an un-airconditioned flat in Singapore in our calculations?), and we of course don't want a fan . . . it's plain to see the bar-tab for transformer and heat-sink is getting pretty hefty.

When I say a Class B amp could be "better in some ways", I'm thinking about all the other things I could, as an amplifier designer, spend the customer's money on to improve the sound, other than a brute-force approach to linearizing the output stage. If I'm clever enough to get similar performance results from from a Class B output stage (yes I know this is a significant challange), I can definately build a better amp for a given amount of resources.

A great comparison is Levinson ML-2s and the ML-3. I've had both amps in my system for a bit, and enjoyed the latter much more . . . the ML-2s were like a high-maintainance chick that looked gorgeous on your arm, but didn't know how to have fun when you got home and turned the lights out.

Kirkus - Thanks, it makes sense.

the ML-2s were like a high-maintainance chick that looked gorgeous on your arm, but didn't know how to have fun when you got home and turned the lights out.

Kirkus,

How about a design that runs Class A to two thirds power? Is that like a gorgeous chick that also knows how to have fun when the lights are out?