#2
It's quite technical. In short I think it depends on the way the power tubes are biased.

In VERY short, 99% of amps out there with more than 1 power tube will be class A/B.

Vox AC30s/15s are class A/Bs, not class A.
#3
as far as I've heard, it's all about the output of the circuitry and stuff....
I've never really had it put in a way that I understand...
#4
For a guitar player, there is no use in knowing what it means. If you're really interested in the technical aspects of amps, buy a book about it (I recommend 'the guitar amp handbook').
#5
Exactly. An amp will sound like it sounds. Class A or A/B... meh. Just play it and it'll tell you what you should need.
#7
Here you goSubject:
Re: class a or ab?
01/30/2004


--------------------------------------------------------------------------------

versaln...

Class A amplifiers have a single-ended device (i.e. a single transistor, tube, etc) that amplifies the entire signal.

Class AB amplifiers have two devices (i.e. transistors or tubes) that amplify 1/2 of the signal each. In other words they share the load.

Audio purists will tell you that the Class AB distorts the signal. This distortion is what is called "crossover distortion" and it occurs when the device doing the amplification shuts down and allows the other device to pick up where it left off. Todays Class AB amps have, virtually, no crossover distortion - or, at least, crossover distortion that you could hear w/ your ears.

Class AB amps are, by their nature, a bit more conservative in terms of power consumed per power output. In other words, they're more efficient. Their output stages tend to run cooler, and last longer than their Class A counterparts.

Does it make a difference today? Purists will tell you yes... most folks can't tell the difference...

Grab a couple of each one and play them... see what you think... and then choose the one that makes you feel good.
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#8
It IS possible for an amp with mutliple power valves to be class A. It is not about the amount of power valves. It's a lot more complex than that. I honestly don't know much more details about this though...
#9
Quote by mr_hankey
For a guitar player, there is no use in knowing what it means. If you're really interested in the technical aspects of amps, buy a book about it (I recommend 'the guitar amp handbook').

completely agreed
i had the basics about what each one is explained to me one time, and it really didnt help me that much
as long as you dont wanna build an amp yourself (say a new design) you dont really need it

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#10
This is all you really need to know:

An amplifier where the power section is working at a 100% duty cycle (therefore amplifying the entire signal, the entire time) is considered to be a class A amp. True class A generally references a single ended design as opposed to the push-pull designs common today.

Class B is where there are 2 (or a multiple of 2) items in the power section and each half of them is operating at an exact 50% duty cycle (amplifying half of the signal each). However this design has some problems dealing with syncing the transition between halves of the power section creating what is called crossover distortion.

Class AB is the answer to crossover distortion. By biasing the power section to be slightly on during it's usual off cycle you end up with a less severe transition between halves of the power section. Therefore a Class AB amplifier runs a duty cycle of somewhere higher than 50% but less than 100% depending upon the bias.

There's more to it than that, but unless you're designing amps it really isn't that important.
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#11
all there is to add is that class b would grant the "best" amplification but its physically impossible to find/build 2 exactly identical tubes which you'd need for tht

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#12
Quote by hendriko
all there is to add is that class b would grant the "best" amplification but its physically impossible to find/build 2 exactly identical tubes which you'd need for tht

don't you mean a ?
#13
Quote by The red Strat.
don't you mean a ?


No. Class A is very inefficient, and requires bigger and more expensive transformers.
#14
Quote by mr_hankey
No. Class A is very inefficient, and requires bigger and more expensive transformers.

yes, i know that. but he said 'best' amplification, isn't that technically class A ?
for sound that is, if we're talking about the best amplification meaning most power then obviously B is best.

i think i understood hendriko wrong
#15
Best is what YOU make of it as far as sound is concerned.
#16
Class =/= anything important.

I've been researching it for ages and it's almost ridiculously complex.

It doesn't matter, is what I would say.
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#18
Quote by The red Strat.
yes, i know that. but he said 'best' amplification, isn't that technically class A ?
for sound that is, if we're talking about the best amplification meaning most power then obviously B is best.

i think i understood hendriko wrong

thats what i meant...couldnt think of the word, my appologies

so, Class A is about 50% efficient
class B (ideally - like said, its almost impossible to find 2 completely identical tubes) about 66% and Class AB somewhere in between

same goes for power

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