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
onhwy61's avatar
onhwy61
5,134 posts
 
You're not wrong, but what's your point?  Knowing how many class A watts an amp can provide is useful info.
erik_squires OP
15,626 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

stevecham
3,340 posts
 
Kosst: you can have push/pull Class A if the devices operate their 360 degrees of duty cycle out of phase of one another.
three_easy_payments's avatar
three_easy_payments
2,097 posts
 
I guess that's the nice thing about my Cary 120 (and other Carys) - it's a Class AB, push-pull amplifier, but operates in Triode (Class A) or Ultralinear (Class AB) mode with a switch.  No ambiguity or point of departure that isn't deliberate.
helomech
1,482 posts
 
Yes and no. Some AB amps are capable of practically zero power as class A.
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