Class A Power in A/B amplifiers?

What I meant to say that my own ears have yet to discern a preference of Class A over Class A/B or even D which is even moderately consistent.

:) This is an entirely different issue! If the amp has feedback, you'll probably not be able to tell anything about class A or AB. If the amp is zero feedback you will. Most amps that are class A or AB and run feedback simply don't run enough, so you'll get artifacts on that account (usually brightness and harshness caused by distortion). Pretty hard to tell which is which when that issue is overshadowing things.

Personally I find the arguments for/against Class A on technical terms alone lack overwhelming evidence.

@erik_squires The arguments are twofold for which there is a lot of evidence if not proof. The first is that you can bias the device in its most linear region. Given that most amps tube or solid state can't really be given the feedback they really need, this is a useful means of allegedly not having to have so much feedback to build a linear amplifier because distortion is lower to start with.


The second issue is that you get more accurate even ordered harmonic cancellation when both output devices are operating in the A region. With the even orders cancelled, there is less overall distortion and so the odd orders tend to be at a lower value (this particular aspect is more useful if the amplifier employs the push-pull/differential operation from input to output). This again is helping for the fact that its likely that insufficient feedback will be applied to the circuit.

There really is no such class as Class AB, it is used to describe the mode of operation when a Class A amp hits a low impedance and one of the pairs of output transistors stops conducting.

This statement is false. Class AB is defined as any push-pull amplifier which is class A at lower power (which is done to prevent artifacts at the zero crossing point) and class B at higher power. The *amount* of class A power is undefined.
Types of amplifier class:
Class A1, A2 and A3 (the latter recently develeped)
Class AB (which includes class AB1 and AB2)Class B
Class C (only used in RF power amplifiers)
Class D (doesn’t refer to digital; ’D’ was simply the next letter- the first commercial class D amps were made in the 1960s)
Class E (switching RF amplifier)
Class F (harmonically tuned RF amplifier)
Class G (modified A or AB amp; IIRC first used by Hitachi)
and on and on...

Is there a general industry standard for the amount of Class A power in Class A/B amplifiers?For instance SimAudio has always touted that they run Class A for the first 5 watts.

No. If the amp is only 1/4 or 1/2 watt before it goes into B operation its still considered class AB. Some amps out there have what is marketed as 'enriched A' operation where they have 20% or so of full power in the A region, but that is only marketing; such amps are still considered class AB. There is no such thing as 'A/AB' unless there is a switch to differentiate the two.