equating class A to class AB SS amps?

Excellent answers, I always wondered about this too.

Thanks.

I owned an Aleph 30 (Class A) amp rated at 30 glorious watts per channel. Based on the different amps I have owned previously and a direct comparison to them, it had no more power than just a 30 watt per channel AB solid state amp.

Many thanks for all the helpful replies! Now I am less confused.

The speakers that I am considering are the Verity Audio Parsifal Ovations, driven by either a Luxman 590Aii or a 509u. Both Luxman integrateds are heavy beasts with large transformers/power supplies, and they exactly double their output into 4 ohms. One is class A (590Aii, 30 wpc) and the other class AB (509u, 120 wpc).

The 509u probably operates in class A at low volumes, and may be the way to go. I know that the 590Aii is highly regarded, but I am concerned about a hot and power hungry pure class amp in the long-term.

Adding a Wadia 381 or an Esoteric X-05 cdp to the mix may be the beginning of a great system.

Regards,

Mark

Mark I think the deciding factor should be your ears;if you can bring the 2 Luxman units home with the speakers to see how they interact in your listening room;let them warm up for a set period of time then sit down and enjoy the decision making process.Hopefully you can do a home audition
of the pieces in question;good luck and enjoy the listening.

Mark - When you listen to 200W peaks your class AB amp really delivers to speakers on average only few percent of peak power. It is because music is not always at the peak and half as loud means 1/10 of power. In addition there are gaps (unless you listen to sinewaves). Nobody sane would design power supply in 2x200W amp for 800W required (50% efficiency at best). Typical amp can deliver full power at limited period of time (like 1 minute) before thermal protection kicks in. There is no need to design large heatsinks for the same reason - otherwise they would have to be the same size as in class A amps.

Class A is extremely wasteful but has one big advantage - is more linear before negative feedback is applied. At the end (with feedback) both class A and class AB might have the same linearity but class AB required 20x more gain (before feedback) to achieve this. This huge gain (in order of 4000) in connection with limited response of the amp (limited slew rate) is causing late feedback correction. In time domain it shows as small overshoots of pulses and in frequency domain it shows as enhanced higher order odd harmonics (bright sound). This is called TIM (Transient Intermodulation Distortion) and was unknown until 70's. There are great class AB amps where designer minimized the problem and also some bad class A amplifiers. You have to listen. My general intuition is that better specifications mean worst sound (achieved by deeper feedback). Same with power - what is on the paper is useless. The only usefull parameter you can find there is weight (some correlation with power).