Class A, B, C? What do they mean?

http://forum.audiogon.com/cgi-bin/fr_srch.pl?&1&procsrch&3&4&

The first five or six hits cover you question in various ways. Search "class" in the archives if the above doesn't work.

A few other good posts are:

http://forum.audiogon.com/cgi-bin/fr.pl?htech&1024059614&read&keyw&zzclass=a

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1020620795&read&keyw&zzclass=a

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1019521148&read&keyw&zzclass=a

Just highlight each of these in turn and copy them to the Address bar above. They are some nice past threads on the topic.

I often read "Stereophile class A" amp. It seems Stereophile class A is not the same as "class A bias" amp.

What does "Stereophile Class A" mean for a piece of an equipment?

It's supposed to mean that the equipment reproduces music exceptionally well. The jury is out on that since it might mean that the company advertises in Stereophile exceptionally often.

You are getting confused between technical operational classifications of amplifiers, and Stereophile's completely unrelated subjective ratings systems from their review staff.

Operational classes of amps are not ratings at all, they are just technical descriptions of how the amp operates. Class A operation means that the amp is not in push pull configuration. Class B is Push pull operation. Class A/B operation is when the amp operates in Class A mode up to a certain wattage, and then slips into Class B operation. As far as I know, there is no such thing as class C operation. Class D stands for digital operation, for example, the bell Canto Evo series amps.

Stereophile has a rating system that has nothing to do with the technical operating modes of the amplifiers. They are divided into classes A,B,C, and D. These are subjective qualitative values rating the sound of a unit that has been reviewed. Class A is best and class D is still pretty good. Mid fi components don't even make it on to their ratings system.