Amp that has continuously variable bias?

I thought it was called "sliding bias". A search turned up very little.

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