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A not-so-obvious disadvantage with class A designs is that this high idling current has consequences to the distortion levels far beyond the theoretical elimination of crossover artifacts, (which even in itself is debatable). Transistors have numerous types of distortion mechanisms, among which are deviations from linearity under conditions of simultaneous high voltage and high current. These are, of course, the exact parameters necessary to class A operation, and a typical Class A amplifier runs distortion levels at least 10 times, and often over 100 times, as high as a Class AB amplifier of similar power, or around 0.1%. A careful inspection pf the distortion spectrum also reveals that all the'harmonics are increased, including those represented by the crossover distortion at which the class A operation was aimed in the first place!
It is a curious thing that the new 'cubed Bryston amp series is LESS biased to class A than the squared, yet does sound better.
Pretty sure all First Watt amps are pure Class A. They aren't space heaters either....because they have less generous output, and simpler circuits, than their Pass Labs brethren that switch to A/B. Just saying that a class A amp (or A - A/B switching amp) doesn't necessarily need to be a giant space heater. It fully depends on output in class A and how deeply biased into class A the amp is. Sorry if a little off topic.
http://www.sst.audio/son-of-ampzilla/
I'm aware that certain Parasound amps operate in Class A for perhaps the first 7-9 watts of operation, then transition to Class A/B thereafter.Are there other amps on the market that operate in this manner?