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In Reply to: Class A to B switching nonsense posted by Feanor on April 4, 2014 at 08:47:40:
However, when the amp is leaving Class A it is possible that it will be heard depending on when it moves to AB (actually B because at that point it will cutoff at zero crossing). If the speaker is pretty insensitive and the bias only a few watts then probably quite a bit of listening is done in B or at least at low enough volume levels that the added distortion might be audible.
If you read Boyk and Sussman's simulation paper you will see that MOSFET Class A PP output stages are actually theoretically perfect...real world says otherwise but they get close. When they go into Class B (when the bias runs out so to speak) all hell breaks loose and they distort pretty badly. Funny enough bipolar transistors are less Schizophrenic... they just have quite a bit of distortion all the time unless you use a lot of negative feedback.
A Class A MOSFET single eneded stage is quite interesting because it has only very simple low order harmonics and CANNOT leave Class A (it is single ended afterall).
So, while Nelson is right that it is not so abrupt as to have a "klunk" it might be audible if the amount of Class A is low and the sensitivity of the speaker is also low.
Obviously, an amp that runs 20 watts in Class A will be in Class A most of the time with most speakers.
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Follow Ups
- RE: Class A to B switching nonsense - morricab 12:44:06 04/04/14 (8)
- Let's remember the purpose of class A - Feanor 13:36:57 04/04/14 (7)
- RE: Let's remember the purpose of class A - morricab 04:07:52 04/05/14 (5)
- RE: Let's remember the purpose of class A - rick_m 10:23:09 04/05/14 (1)
- RE: Let's remember the purpose of class A - morricab 12:19:22 04/05/14 (0)
- RE: Let's remember the purpose of class A - Disbeliever 06:35:49 04/05/14 (2)
- RE: Let's remember the purpose of class A - morricab 12:37:50 04/05/14 (1)
- RE: Let's remember the purpose of class A - Disbeliever 00:08:53 04/07/14 (0)
- RE: Let's remember the purpose of class A - RGA 01:21:24 04/05/14 (0)