Amp classes

[jimmy]

What are classes?
I see that different amps have Class A, Class B, Class A/B opperation; but I'm not really sure what all that class stuff means.
Any help would be great.

 

[marvar]

Re: Amp classes

By definition, any Class A amplifier draws maximum plate current at all times, and it should not deviate between idle (quiescent) and full output power. Another way of saying this is that the plate current is flowing at all times. The Class AB amplifier will have its plate current increase approximately 25% between idle and full output, while each tube takes turns 'not conducting'. The same plate current is said to be flowing between 'appreciably more than half and less then the entire electrical cycle'.--
OK! got it now? LOL

 

[jimmy]

Re: Amp classes

By definition, any Class A amplifier draws maximum plate current at all times, and it should not deviate between idle (quiescent) and full output power. Another way of saying this is that the plate current is flowing at all times. The Class AB amplifier will have its plate current increase approximately 25% between idle and full output, while each tube takes turns 'not conducting'. The same plate current is said to be flowing between 'appreciably more than half and less then the entire electrical cycle'.--
OK! got it now? LOL

THANKS! I got it.

 

[Truant]

Re: Amp classes

There's a really good explanation on Mesa's website.

I'd try to explain it, but I'd make an ass of myself. (which isn't hard)

 

[aleclee]

Re: Amp classes

http://www.aikenamps.com/ClassA.htm

 

[jimmy]

Re: Amp classes

http://www.aikenamps.com/ClassA.htm

Looks like I have some homework tonight.:scratchch

 

[Animal]

Re: Amp classes

What I'm more curious about is how all these different classes affect the tone of an amp .etc over than how they actually work.

 

[chcjunior]

Re: Amp classes

What I'm more curious about is how all these different classes affect the tone of an amp .etc over than how they actually work.

That's what I'm curious about. It seems like one (A/B maybe?) would provide more clean headroom while class A would break up sooner?

 

[aleclee]

Re: Amp classes

What I'm more curious about is how all these different classes affect the tone of an amp .etc over than how they actually work.

There's not a lot of tonality that's absolutely attributed to operating class. Other factors such as negative feedback and cathode bias have a bigger impact on tone. In fact, most amps that are described as "Class A" are in fact Class AB (there's another article on Aiken's site about the AC30 being AB) but have no NFB and are cathode biased. That's one reason why I don't refer to the Mesa article. Like most builders these days, they tend to use Class A as a marketing buzzword rather than an accurate technical description of their amps' operating class.