2. amps-preamps
  3. 143178-20253

Is there an actual difference between AB and A/AB ?

Almost all high end linear audiophile power amps which are not pure Class A sell some story about being Class A up until a certain power output, then switching to AB.

Excuse me, but isn't this actually AB to start with?

The whole point of AB is that you run with some bias current to prevent complete transistor shut off at the crossover frequency. This whole "our amp is Class A up until n watts" seems like hype.

Am I wrong?

Best,
E
erik_squires

Showing 3 responses by erik_squires

erik_squires OP
15,878 posts
 
Perhaps audio manufactures should drop the term AB


They have, I think. They say something like "high bias AB" or "A/AB"
The curmudgeon in me wants them to just stick to calling it AB. :)

Let's have a fight over it! ;)

Best,
E


erik_squires OP
15,878 posts
 
You're not wrong, but what's your point? Knowing how many class A watts an amp can provide is useful info.

Hey @onhwy61 - I'm not really making a point, I'm fine with a manufacturer making a claim  to Class A at low power if accurate.


Really I am asking for help fixing a disconnect in my own mind and knowledge. Ages ago, when I took a course in the subject, you had A, or B or A/B.


This new fangled combined labeling of audio amps as A/AB is rather new to me, I just wanted to know if it involved actual engineering differences from AB.

Best,
E

erik_squires OP
15,878 posts
 
Are you saying that amps like Pass Labs do not operate in class A up to a certain wattage or are you just saying that those amps should be called AB not A/AB?

The latter. I mean, the whole point of AB is to avoid the crossover distortion of B, without being as power hungry as A.

You can even dial the distortion up and down with an AB amp. More bias = less distortion = more power at idle.

We used to just call this Class AB.
Lately however we call it "Class A until x watts, then AB"


Best,
E


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