Class A into Class AB

Just starting to use Class D since it’s less heat generation than A etc 
I live in So Fl!

Have used PS AUDIO and Peachtree
v happy esp with z Peachtree 150

Class A/AB and class AB are the same thing. At lower powers the amp is class A and at higher power class B. How much class A depends on the amount of bias and can range from less that a watt to lots of watts which is rare.

But even a low efficiency speaker say 82 dB plays a continuous 82 dB with a watt and that's fairly loud so an amp with just 1 watt class A goes out of class A only on peaks which last only a very short time. So class AB amps are in class A most of the time.

Most amps even those costing 6 figures are class AB and well designed class AB amps sound awfully good these days and have more head room than pure(never go into class AB) class A amps which are extremely rare except for single ended amps which must be class A and single ended amps are very low power.

By the way almost all push/pull class A amps go into AB at very high powers especially into low impedance loads. For instance Class A Pass amps go into AB. But they only give you the class A rating in their ads. They produce twice as much power usually total but it's AB then. The only
 push/pull true class A amp I know of was he old Mark Levinson ML2 which was 25 watts class A into 8 ohms and still class A at 100 watts into 2 ohms.

Then there's the sliding bias amps which could be called class A but some argue they aren't true class A. I'm not going into that discussion.

Hello, 
It is not marketing hype. From what I understand the class A/B switches on and off. This lets you have more watts with less amps. It is more efficient and therefore runs way cooler. Most designers bring in the class A just above or below that point where the switching is so you have better sound and don’t notice the gap. So at normal or regular listening levels you are in Class A. When you go higher or the music becomes more dynamic the class A/B takes over.