#1
First forgive me if this has been discussed before, but I've searched and haven't really found a clear answer (maybe I overlooked it) but here it goes...

Tonally, and practically, what is the difference between "Class A" and "Class A/B"?

I am 99% sure of buying the B-52 AT100 all tube Rectifier head and I was wondering how to use the different Class Tube settings. For instance, is "Class A" better suited for Metal Rhythm, Metal Lead, Classic Rock??? Is "Class A/B" used for Speed Metal or Ozzy Osbourne type metal.

I'm sure I could eventually figure it out on my own but sometimes I dont trust my own ears....LOL

Thanks in advance.
#2
The Class A should have more harmonics and pleasing distortion at lower volume levels, but the bass will be more loose. Class A/B will sound a little tighter, with less harmonics from clipping, and have more head room.

I haven't played the B-52, but I play a Mesa Express, a dual-class amp, which is often compared to it. I use the Class A more for overdriven soloing, cleans and almost-clean tones, and the Class A/B more for higher-gain rhythm work.
#3
I wouldn't worry about it too much unless you find that you absolutely can tell the difference and like the characteristics of a particular one...

Class A pushes the tubes harder and the distortion will be more "spongy" than class A/B or Solid State(there's also a setting for this)...

Class A will have more harmonic tendencies as said above, but it's negligable...

Class A/B works the tubes more efficiently and will preserve tube life more than Class A, and will have a tighter response as well..
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#4
Functionally, a Class A amp draws the same amount of current from the plates whether it's at idle or while playing. Class A/B has points at which the draw is higher, then lower.
#6
it doesnt really matter

if one amp is A and one A/B. theyll be 2 completely different amps any way, so will sound different regardless

dont lose sleep
Get off this damn forum and play your damn guitar.
#7
Why do people always wonder about this?
There's more to an amp's tone than if its Class A or Class A/B.

There's really no defining tonal characteristics in a Class A (or A/B) amp that can be made into a blanket generalization about all Class A (or A/B) amps.

BTW, for the most part, every single tube amp that's over 5 watts these days is usually Class A/B.
#8
Quote by stevo_epi_SG_wo
it doesnt really matter

if one amp is A and one A/B. theyll be 2 completely different amps any way, so will sound different regardless

dont lose sleep



The question isn't about whether the AMP is class A or class A/B...

He was asking specifically about the AT-100, which has 3 switchable modes, Class A, Class A/B, and Solid State..

He was merely asking what difference it would make running this particular amp in each of the classes of operation...
Washburn D-12
Ibanez RG
Ibanez RG 7321
Epiphone Les Paul / EMG 81 85
Fender MIM Ash Stratocaster
Digitech Whammy
Small Stone Phaser
Boss SD-1-Modded
Boss MT-2-Modded
Boss CE-5
Boss DD-3-Modded
ISP Decimator
B-52 AT-212
#10
^whether or not it runs in true class A or not really doesn't matter... There are still defining characteristics that seperate the modes of operation. This community would not be much of a help if everyone said you should go figure it out yourself...
Washburn D-12
Ibanez RG
Ibanez RG 7321
Epiphone Les Paul / EMG 81 85
Fender MIM Ash Stratocaster
Digitech Whammy
Small Stone Phaser
Boss SD-1-Modded
Boss MT-2-Modded
Boss CE-5
Boss DD-3-Modded
ISP Decimator
B-52 AT-212
#11
^For this amp, yes. Those modes probably do sound different.

For amps in general, no. Class isn't that way to define the tone. The overall circuit has more to do with the tone.

And while I see what you're saying about the community, this IS something he should figure out for himself. It's all about his personal taste. What he may think is good for a metal tone may not be what I think is good for a metal tone.