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!



A watt is a watt is a watt. It costs a lot more to build a pure class A amp than a class AB amp of the same power. Class A amps are very inefficient, need large transformers (power and output, if applicable), and dissipate a lot of heat.

For all their disadvantages, Class A amps often have a kind of liquidity that is hard to find in Class AB designs.

Class A amps go into clipping more gracefully than class AB amps. This sometimes leads users to push the class A amp hard into a load because of the gradual move into distortion (and largely 2nd harmonic distortion at first, which is pleasing to the ear).

So the L-509u is capable of much more power than the L-590Aii. There is one more factor to consider, though, and that is how the two amps behave as the load impedance changes. Speaker impedance often varies across the frequency spectrum, and it's not clear how well the two amps deliver current to lower impedances. Class A amps often but not always have an edge here due to their large power supplies and basic topology.

If you are using efficient speakers consider the L-590Aii. It will emphasize finesse over brute force.
An amplifier is a tool to drive your speakers, select them first and the select an appropriate one that you like the sound of on THAT speaker. There are many factors involved, ghostrider has pointed several of them out. Generalizations about the qualities of Class A, Class B, Tubes etc. are less important than the qualities of a particular amp and how well it matches your speaker.
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