#4
what do you mean by class?

It's AB, if that's what you're looking for.
I'm putting my GAS on hold
for a couple months in order to pimp my ride.


Don't judge me.
#6
Yeah, well...I found a Mark IV. An epic NGD thread is coming.
I'm putting my GAS on hold
for a couple months in order to pimp my ride.


Don't judge me.
#8
to the TS: it's probably class AB of some variety, probably juuust stretching into class AB2. No one really makes a class A amp, unless it's a Single Ended (champ, Valve JR, etc)...

And no, the AC30 is NOT class A.

*stalks away muttering about marketing bull**** under his breath*
Quote by kcdakrt
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#10
um..it's 6:30am where I am right now and I haven't had any coffee, so you may want to google this to make sure, but I'm going to take a crack at it.

Class A means that all tubes conduct the entire time. Basically, it's kindof how you'd expect an amp to work...two output tubes, one "pushing" the speaker and one "pulling" (hence the term push-pull poweramps). Single ended amps are by nature class A (there's been contention on this topic for some time, as when you drive the tube to clipping it stops conducting, so now it's not Class A...maybe. I think it still qualifies).

Class AB means that one of the tubes is turned "off" during part of the signal cycle. That is, one tube pushes the speaker out. Speaker relaxes back to center. Other tube turns on, pulls speaker back, etc etc. Depending on how it's biased and a bunch of other things, the tubes can be off for significant amounts of time of the signal cycle (each tube would be off 40% of the time) or way less (5% of the time).

Class B means that each tube is only turned on by itself. (think AB but with each tube off 50% of the time).

The number after the class is whether or not grid current flows. 1 = no, 2 = yes.

OK, techno mumbo-jumbo out of the way, how does it sound?

Class AB is what your standard amp runs in. It's better efficiency (you can get more wattage out per tube compared to class A), it sounds like how you'd expect an amp to sound. There is a hint of distortion when one tube switches off and the other stays on, called crossover distortion. If kept to a minimum, this serves to warm the tone up. One of the "features" of AB is that there is less current needed by the output tubes at idle than at full-bore. So, when you go full bore, the power supply can struggle to keep up (if it has a tube recto), the voltage drops, and you get compression (the classic, tube recto "sag").

Class B isn't used much that I've seen.

Class A lacks crossover distortion so the tone sometimes isn't as warm (that can be made up for in the preamp though). The current also remains the same during idle and full-bore, so you get no sag, regardless of tube recto.

...Class A isn't all it's cracked up to be, huh? Most of it is the Vox AC30, which was claimed to be class A, getting famous and popular and all the other "kids" wanting to be like the cool kid, so they just made up some marketing bull**** and here we are.

In actuality, most tube amp manufacturers would never make an amp so inefficient as to run Class A, so if you hear any BS about an amp being Class A, either they're lying or it's single ended.

The one place Class A has a really good application is with metal players (my metal amp I built up runs straight class A). That's because there is no crossover distortion or power supply sag, so it's a very "tight" and controlled sound, which works well with metal.

Oh, regarding the 1 or 2...to really drive it into 2, you really need to add another tube per pair of output tubes, something that cuts into profit margins, so most amps run 1 and sort-of flirt with 2 at high volume levels. Doesn't matter a whole bunch though.
Quote by kcdakrt
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