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equating class A to class AB SS amps?

I am confused about how to equate and compare class A to class AB solid state amps. Is there a conversion factor, or is it not that simple? I have heard people say that "this 30 wpc class A amp is easily equivalent to 150 wpc class AB" etc.

The two top Luxman integrated amps cost about the same. One is the 30 wpc pure class A L-590Aii, and the other is the 120 wpc class AB L-509u. How do these amps equate or compare to each other? Which is more powerful (or are they about the same?)? I am confused!

Regards,

Mark

toronto416
elizabeth
6,726 posts
 
Big watts.. little tiny watts. Tubes have BIG watts... Class A amps usually have BIG watts because they have big power supplies..
Cheap class AB amps have little tiny watts, unless they are BIG, really BIG (and expensive).. and can double the wattage with halving the impedence. (Think Bryston 28B-SST*)
But really a Watt is a Watt. (though some small amps cheat and claim they have more: that is the 'little' watt side of the story.
Really a 50 watt amp only puts out 50 watts into 8 ohms, and a 200 watt amp puts out 200 watts into 8 ohms. BUT!! that 50 watt amp may put out 100 watts into 4 ohms and 200 watts into 2 ohms.. (a few such heroic amps can do 400 watts into 1 ohm) but the 200 watt into 8 ohm amp may only put out 250 watts into 4 ohms and actually fizzle to less than 100 watts into 2 ohms, and explode (blow the fuses) when it sees a 1 ohm load.
This is only to confuse you as the power handling ind low imepdence loads has NOTHING to do with class "A" or class AB
However it all fits into the big picture of how power amps are rated.
seditious3
183 posts
 
The other point is that many AB amps operate in class A until a certain wattage is reached, then go AB.

I used to have a 75 watt (into 8 ohms) class A amp that was beautiful to listen to.
macdadtexas
1,794 posts
 
Excellent answers, I always wondered about this too.

Thanks.
phd
1,008 posts
 
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.
toronto416 OP
133 posts
 
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
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