What could I expect to hear from a Class A amp?

Kijanki, this waiting does happen during the day, on the weekend as well. You are correct about me being picky. Yet it seems that if I want to get the typical benefit of class A, I'll have to wait. Otherwise it sounds closer to my former class AB amplifier which is not bad really.

I use a class a amp with 88db 4ohm speakers and it is definately worth it imho. My experience is that it takes 45 minutes to warm up with improvements up to 4 hours. I leave the amp in "standby" mode and never turn it off. Standby does not generate heat but keeps enough current that it doesn't experience a cold start. It generates 150W into 8 ohms 300W into 4 ohms and 600W into 2ohms. It will play ear crushingly loud. Compared to ab amps I've had it has more low level detail and never shows a hint of strain even with the minimum impedance of 2.5 ohms on my speakers. With any given setup any given individual may prefer a different set up and few generalizations can be made. My personal belief is that properly executed ss amps with large power supplies capable of doubling down far more than their ab counterparts with much smaller power supplies are ideal for high impedance loads with reasonable sensitivity. - jim

Hey, I already said, the XA-100.5 monos did 115 dB without ever choking up on
any dynamic swing, and the X-600.5 never gassed out on heavy bass runs. The
needle never moved, staying class A. It blows your hair back, and to think they
are working a 1 ohm load throughout. The long ribbons never get warm.

I'm not sure I understand, though, why Class A would run cooler when outputting signal into a load. It's tempting to think that could result from a portion of the current that would otherwise flow through some of the output transistors (at zero signal conditions), being diverted through the speaker instead.

Yes that is the reason. At no load (or I meant to say no input signal) you are actually running at 50% current output and all that current has to be dissipated internally in the amp somewhere, across the bias circuit if you will (it is the high bias that makes the current flow at 50% when at zero input signal). When you play music the +ve signal requires more current (but it all dissipates in the speaker) and on the -ve cycle it actually diverts current from the bias circuit to the speaker (meaning the amp generates less heat).

The amp may use more power from the AC but it will likely run a bit cooler - no enormous difference and I gues it may vary a bit on the exact topology and type of output devices.

Thanks, Shadorne. I subsequently found this article by Nelson Pass, which appeared in "Audio" magazine in 1977. Figures 1 and 2 enabled me to visualize what you were saying:

http://www.passdiy.com/pdf/classa_amp.pdf

The article also contains the following interesting statements, relating to the original poster's questions:

The usual total harmonic and intermodulation distortion figures do not reveal the abrupt output stage distortions accurately because of the averaging factor involved in such measurements. A spike of crossover distortion may reach 2 per cent, but if it occurs only over 5 per cent of the waveform, it averages out to a respectable 0.1 per cent distortion figure. Considering this error factor, it is easy to see why two amplifiers with the same specifications can sound so different. To properly evaluate the distortion, peak distortion and harmonic distribution must be considered. Typical class A amplifiers will exhibit low order harmonics, and their peak distortion is less than twice the average distortion. In class AB amplifiers, very high orders of harmonics occur, and the peak distortion can be as much as thirty times the average distortion.

Another problem common to class B and AB output stages is due to the unequal turn-on/turn-off times of the transistors. Because the turn-off time is greater, both transistor sets can conduct uncontrollably under high slew conditions, making it dangerous to operate the amplifier at high frequencies, a particularly bad problem with some quasi-complementary designs. In a class A output stage, however, there are no abrupt nonlinearities and no turn-on/turn-off delays. The smooth transfer characteristic yields low order harmonic distortions, and these harmonics can easily become unmeasurable at low power levels.

Regards,
-- Al