Explain Amp classes & how effects sound?

I see class A, B, AB, Class T, etc on amplifier specifications. Can someone explain (simple terms) how each class (even class T) effects sound quality?
What about class H. Soundcraftsman had some amps in the 80's class H. I had one and ran it HARD! Never got more than just a tad warm! I guess the design never took off.
Also class D had NOTHING to do wit digital. Many people presume wrongly that the D stands for digital. This is just not true.

There are amps being sold as class A but in truth some of these are Class AB with a high class A bias. But how much watt do you really need? I just spoke with someone who ones 1000watt mono amps. He never saw the needles move beyond 15 watt and normally not beyong 5 to 10 watt.
Mordante comments about class A marketed amps really falling to class A/B is important. IME there is a notable difference with many of these amps when they drop down into class A/B in terms of performance and sound characteristics. Personally, I am a believe in pure class A amps (ie. that remain in class A at all times), but I think this is a matter of opinion. Also, I am not suggesting that all class A amps are better than all Class A/B or D amps (for that matter).

How much power does one really need? That is always the question and there are so many factors that come into play. Obviously the speakers, the room, listening levels, even types of music and of course sound preferences.

I own a pair of speakers that are rated at a solid 8 ohms and the reviewer and printed/promoted mfg. recommended power is 60 wpc at 8 ohms.

However, based on direct communications with the designer of the speakers, he clearly suggests that the speakers operate in a range of 8-16 ohms and based on their design principles are relatively hard to drive. He suggests that for best performance, 200-300 wpc (rated at 8 ohms) will produce the best results. I would agree with his assessment as I have run the speakers with various amps that ranged from a low power SET design, mid power push pull design, mid power 100% class A design and now a higher power 100% class A design (rated at only 125 wpc into 8 ohms). Each power increase proved to deliver better performance in specific scenarios.

Can one have too much power? No, I have never experienced that problem. But I suggest that there needs to be a balance between just a lot of power and the quality of power. Is 1000 wpc monoblocks too much power? Depends on the speakers, room, etc. . . Just because the proverbial needle doesn't ever "seem" to go past 15 watts does not mean for a second that all that is needed is a 15 wpc amplifier or that the 1000 wpc amp is a waste.

I can pretty confidently say that if you have two identifcally designed amps (with the exception of power output) that in the referenced case (above here and by Mordante), the 15 wpc amp will suffer versus the 1000 wpc amp and very, very likely run out of headroom and produce notibly different sonic attributes.
What about class B. The Makamichi 620 was (is) a 'pure' class B amp, delivering 100 w/ch and sounds mighty good. I think that the Quad 44 is also a class B, albeit called a 'current dumping' design, whatever that is!

Salut, Bob p.
Most transistor amplifiers do operate pretty close to class B; at low power levels most of the power comes from the driver transistors rather than the outputs. But in order to keep the amplifier from making significant distortion (notch and crossover) at the zero crossing point, they have to have a certain minimum amount of bias current to make that happen. As a result they are considered class AB.