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Class A into Class AB

I’m still a little confused about power amplifiers and integrated amplifiers that are class A & class A/B. Like when they say the first 8 watts are class A then it goes into 400watts class A/B. But the same amplifier can be biased to put out 12watts class A then go into 250watts class A/B. It can be biased again for 18watts class A and 150watts class A/B. etc. Ive read that these amplifiers, ones that can be biased like that...and in general all the "first X amount of watts are class A before going into class A/B"...that those first X amount of class A watts is NOT true class A. If that’s true...what is it then? What’s "kind of" class A mean? What’s the point of a "first X amount of watts are class A" then?

tmac1700

Showing 1 response by twoleftears

twoleftears's avatar
twoleftears
5,320 posts
 

So let me get this straight.

You can design amps that only operate in class A.  When pushed to their limit they simply distort.

There are amps that slide from class A to class AB (e.g. Pass XA25, Luxman).

There are amps that can be produced with different amounts of class A before transitioning to class AB (e.g. Coda).

There are amps that have a switch that allows you to choose between class A and class AB operation (example?).

Does that cover it?

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