Amp that has continuously variable bias?


Excuse me if this has been covered before.
Is there a power amp that varies the bias according to what the power demands are? When the speakers are demanding more current , the amp will up the bias to remain in class A, and when the current demand is low, the amp will decrease the bias to save energy and reduce heat.
I know that many amps remain in class A up to a certain level, but that's not what I'm referring to.
Is this what the Krells do? Any others?
rubber

Showing 1 response by aball

What you are talking about is called "sliding bias." Some of the Krells do this (the ones with names that end in an "S") although I don't think the new ones do. YBA also uses this scheme and a few others that I can't think of right now.

It is a good idea but hard to execute - that's why it isn't commonly used. I remember reading that some magazine reviewers weren't big fans of Krell's sliding bias amps, saying that large-scale dynamics were compromised. But I know the YBA amps sound fantastic so it is doable.

Arthur