Is there an actual difference between AB and A/AB ?

It’s simply the bias on the output devices that determines the level of power afforded in Class A. Such bias allows, or not, whether the output device can swing a given power level through the entire 360 degrees of the duty cycle. The limiting factor is heat and this must be managed effectively, otherwise, the device will fail, sometimes catastrophically.

Are you saying that amps like Pass Labs do not operate in class A up to a certain wattage or are you just saying that those amps should be called AB not A/AB?

The latter. I mean, the whole point of AB is to avoid the crossover distortion of B, without being as power hungry as A.

You can even dial the distortion up and down with an AB amp. More bias = less distortion = more power at idle.

We used to just call this Class AB.
Lately however we call it "Class A until x watts, then AB"


Best,
E

You're not wrong, but what's your point?  Knowing how many class A watts an amp can provide is useful info.

You're not wrong, but what's your point? Knowing how many class A watts an amp can provide is useful info.

Hey @onhwy61 - I'm not really making a point, I'm fine with a manufacturer making a claim  to Class A at low power if accurate.


Really I am asking for help fixing a disconnect in my own mind and knowledge. Ages ago, when I took a course in the subject, you had A, or B or A/B.


This new fangled combined labeling of audio amps as A/AB is rather new to me, I just wanted to know if it involved actual engineering differences from AB.

Best,
E