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P.S. Can anyone explain to me what a Class A amp is, and why this
matters? I understand that some guitarists prefer them for the way
they distort. My amp is a Hot Rod Deluxe, which I think is not a Class
A amp.
Just curious!!!
--- In , "windanseabeachboy
<gavinehringer@m...>" <gavinehringer@m...> wrote:
> P.S. Can anyone explain to me what a Class A amp is, and why this
> matters? I understand that some guitarists prefer them for the way
> they distort. My amp is a Hot Rod Deluxe, which I think is not a
Class
> A amp.
>
> Just curious!!!
Ya'll asked for it!
Class A is an overused term that refers to the biasing of an
amplifier stage. A class A amplifier output device (tube or
transistor) always has current flowing through it (never turns all the
way off) over the whole signal waveform. A class B amp output device
can turn all the way off when it it is not putting out that part of
the waveform. This usually refers to a "push-pull" amp where one tube
(or transistor) make the positive voltages and the other makes the
negative voltages. Class AB is a push-pull amp where the negative tube
(or trans) stays on for part of the positive wavefor and vice versa.
This was significant due to the marked increase in non-linearity
(distortion) of the device (tube or trans) right at the point where it
turned off.
All fender amps with two or more output tubes (incl. the HRD) are
class AB bias. The VOX AC30 is often reffered to as class A. I don't
know if it truly is. Single ended amp's, like the fender champ, are
class A by nature becase the single tube has to be on over the whole
waveform. Class A or B is not a measure of quality (McIntosh, regarded
by many as the finest tube hi-fi amps are class B).
Class A, B or AB does not matter for guitar amps (although your
fender will sound like crap if crank the bias setting down so it runs
class B). Getting the tone you like is all that is important.
best
Dan
