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In Reply to: RE: Quotes from Nelson Pass posted by Feanor on February 03, 2022 at 13:34:11
"What might be fair to say is that A/B amps don't cease being class A when more power is demanded: only the peaks, '+' or '-' of the signal operate in class B mode. There is nothing magical about the shifting."
Then the definitions (and distinctions between) of Class A and Class B and Class A/B have lost their meanings.
I think Pass said what he said, the way he said it, just to get a point across to the non technical reader.
I think he was really saying something like this,
The amp is not Class A at low power but it has something in common with a Class A amplifier, the output devices don't reach cutoff (***like in a Class A amplifier***) when at low power. The amp is not Class B but it has something in common with a Class B amplifier when at higher power levels, the output devices do reach cutoff (***like in a Class B amplifier***).
But just because those two thing are "like" Class A and Class B that doesn't make the amplifier a Class A or a Class B amplifier. It is neither, it is a Class A/B amplifier. Class A/B amplifier are there own thing. Nelson was just trying to get non technical people to understand how they do what they do. He was not trying to re-define the meaning of Class A and Class B or Class A/B. All three are already well defined.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
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It would appear that you have a new definition of amp classes because Nelson Pass is spot on when it comes to the original definition of Class A, AB and B.
I think I get what you are saying.
In order for class A and B to integrate into A/B, the basis for each is there, but they never truly work as pure now that they are called upon to work together vs how they would work on their own.
It would be like asking an 8 cylinder motor in 4 cylinder variable management mode for better gas mileage, response and RPM's, to give you the identical benefit of a pure 4 cylinder motor. Close but not quite the same.
Motor analogy aside, I wonder if the class B portion of A/B is also somewhat less pure and perhaps audibly different vs a pure class B amp at high volumes.
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
nt
Dmitri Shostakovich
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