2. amps-preamps
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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 2 responses by atmasphere

atmasphere's avatar
atmasphere
11,575 posts
 
Perhaps audio manufactures should drop the term AB and adopt A/AB to give consumers more info on how the amp operates. What are the benefits/drawback of two identical 100w amplifier but one is biased for the first 10w in Class A (A/AB = 10/90) whereas the other is class AB from the get go (A/AB = 0/100).
The problem is that there is not established standard for A/AB... its purely marketing. Its not misleading if the manufacturer says it transitions from A to AB at a certain power level, but the result is its still class AB.

The curmudgeon in me wants them to just stick to calling it AB. :)
And that curmudgeon would be 100% correct.


atmasphere's avatar
atmasphere
11,575 posts
 
No- you got it. If its not class A, then its AB (or in some rare cases, B). There is also AB1 and AB2 (which mostly applies to tubes depending on whether grid current exists in the output tubes during part of the waveform).
But there is no such thing as A/AB; that is strictly a marketing term.
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