what is diff: Class "A", "A/B", and "B"

Amplifier Design Principles

This section will detail design philosophies of amplifiers and the various classes of amplifiers applied in audio. For example:

Class A - transistor amp conducts for the entire cycle of input signal, conduction angle 360 deg. Runs hot, as the transistors in the power amp are on all the time, but has high sound quality.

Class B - positive and negative halves of the signal dealt with by different parts of the circuit, the output devices switching continually. Runs cooler, but the sound is not as pure.

Class AB - biasing the transistor amp at a non-zero DC current much smaller than the peek current of the signal source. Second transistor conducts during negative half cycle of waveform and the currents from the 2 transistors are combined at the load. A compromise between sound quality of Class A and efficiency of Class B. Most amp designs employ this method.

This is a direct copy from the Audioholics web site.

Perhaps this will help resolve the explanations. In class A, the output devices conduct more or less as the input varies, but never cut off. In other classes, output stages can be cut off (not conducting) during art of the input signal variation while the other half are conducting. That is why one could say that "different parts" of the signal are being handled by "different parts" of the circuitry. This is not a precise technical explanation, but intended to resolve the verbage. The real deal performance wise is whether the output stage is operating on the most linear portion of its characteristic curve. In class A, they are. :)

It is indeed Hitachi I have. Is this a good thing? Apparently it didn't do so well, or was it not cost effective? Please forgive my ignorance, I've had this thing for twenty years + or - and I've never had any info about it.

I'll think about this over a USDA Class A sirloin steak.