Class A SE vs Class A PP?

[tbryanh]

What are the sonic differences between Class A PAs with either single ended tubes or with push pull tubes?

[kldguitar]

It is class AB

What are the sonic differences between Class A PAs with either single ended tubes or with push pull tubes?

push pull is Class AB

[Enzo]

No, that is not true. SIngle ended versus push pull is a separate issue from class of operation. Most p-p amps you see are class AB, but that is by choice, not by necessity. There are class A p-p amp out there.

A class AB single ended amp would sound awful, but you could make one. P-p amps are either class, both are on the market. SOme p-p amps are even more or less class B amps.

[Paul P]

push pull is Class AB

I don't believe this is correct. Push-pull class A is when both tubes are
conducting all the time but doing so in opposition. When one tube is
pushing the other is pulling. I'd say that push-pull in class A is more
"push-pull" than in class AB because in the latter the tubes (at sufficient
volume) take turns in shutting off for part of the cycle whereas in class A
the tubes are pushing and pulling all the time. I find push-pull class A
pretty elegant in its symmetry.

I can't say what the tonal differences are but one thing is for sure, the
push-pull will be louder :-) I do intend to experiment with this in the
not too distant future as I'm also interested in hearing what the differences
might be. The even-order harmonics are supposed to be reduced by
cancelling out in the output transformer which may not be a good thing in
a guitar amp since these are the "good" harmonics. It may be better to
go with two output tubes in parallel instead of push-pull, another thing I'd
like to try out.

Paul P

[d95err]

The significance of the class of operation in guitar amps is generally very exagerrated. The big confusion is because some classic like the Vox AC30 or Fender "Tweed" Deluxe are often mislabeled as Class A, when they are actually Class AB. Two factors that contribute infinately more to the sound of these amps are:

1. No negative feeback loop around the poweramp
2. Cathode bias

Since the terms cathode bias and negative feedback are too technical for most people, manufacturers (in particular "boutique" builders) have found Class A a much more convenient term to use in marketing.

So, back to the original question - what are the sonic differences between SE PP? Well, not much unless we go into hifi territory. However, the PP amp needs a phase inverter. This will affect the sound (in particularly when pushed).

So essentially you can never compare two amps just by looking at the poweramp; you need to see the whole picture.

[Satamax]

Well, from what i've read, push pull class A cancels 2nd order harmonics, while class A SE doesn't.

[MWJB]

What d95err & Satamax say.

Usually SE guitar amps are built to be chaep (compared to PP counterparts) rather than for any tonal reason...if 4-5W is enough go SE, if you need significantly more go PP.

[tbryanh]

Well, from what i've read, push pull class A cancels 2nd order harmonics, while class A SE doesn't.

This answer sounds simple and clear.

That answer is making me wonder what are the tonal differences between Class A PP and Class AB PP?

[Enzo]

A class AB amp stage will be operating in class A until the signal level gets large enough to turn one tube then the other off for portions of the waveform. Class A conducts all the time, class B half the wave, the remainder in cutoff. Class AB is in between, so whatever the portion of the wave in excess of 50% it takes to turn off one side is hte portion that is running in class A. SO whatever tonal shift might occur at that threshold is the answer.

[kldguitar]

who have drawing about Class A p-p

A class AB amp stage will be operating in class A until the signal level gets large enough to turn one tube then the other off for portions of the waveform. Class A conducts all the time, class B half the wave, the remainder in cutoff. Class AB is in between, so whatever the portion of the wave in excess of 50% it takes to turn off one side is hte portion that is running in class A. SO whatever tonal shift might occur at that threshold is the answer.

Who have drawing of Class A pp and SE, Class se is easy understand.but PP is difficult to understand only by words. Are the two tube parallel, use two tube amp current?But it not pull and push

[Satamax]

Who have drawing of Class A pp and SE, Class se is easy understand.but PP is difficult to understand only by words. Are the two tube parallel, use two tube amp current?But it not pull and push

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

[kldguitar]

which amp use class a PP

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

which amp use class A pp?

[kldguitar]

does class a pp used in guitar amp more ?

I don't believe this is correct. Push-pull class A is when both tubes are
conducting all the time but doing so in opposition. When one tube is
pushing the other is pulling. I'd say that push-pull in class A is more
"push-pull" than in class AB because in the latter the tubes (at sufficient
volume) take turns in shutting off for part of the cycle whereas in class A
the tubes are pushing and pulling all the time. I find push-pull class A
pretty elegant in its symmetry.

I can't say what the tonal differences are but one thing is for sure, the
push-pull will be louder :-) I do intend to experiment with this in the
not too distant future as I'm also interested in hearing what the differences
might be. The even-order harmonics are supposed to be reduced by
cancelling out in the output transformer which may not be a good thing in
a guitar amp since these are the "good" harmonics. It may be better to
go with two output tubes in parallel instead of push-pull, another thing I'd
like to try out.

Paul P

It seems Class a PP used in guitar amp fewer.
which amps used this way?

[Paul P]

It seems Class a PP used in guitar amp fewer.
which amps used this way?

I don't think there are any, at least not mass-produced ones. They seem to
be fairly common in the hi-fi world.

Paul P

[Enzo]

I can't recall, it seems a few are marketed as class A. It is a matter of bias.