Single-ended OR push-pull?

[kacernator]

Hi,

I have decided to build Mikaels Abdellahs SE KT88. But SE OPT are very expensive (I can get just Hammond 1628SEA). PP OPT are half the price of SE OPT.

I am going for the sound, but does SE has so much benefits that are worth the expensive OPTs?

[Hi-Q]

Hi, I always thought that SE transformers were more expensive because they have to be constructed to avoid saturation of the core by the standing current of the output Tube. With P-P the currents in each half cancel each other and hence minimal core saturation.
My personal view is that SE is probably the best way to go with class A but if I was going P-P then it would be strictly using Triodes only.
Les

[SY]

That's a matter of some debate.

From an objective POV, single-ended amps perform far less accurately than push-pull. They impart distinctive signature to the sound (non-flat frequency response, high distortion). If that's what you want, and LOTS of people want that, go for it. The distortions and frequency response abberrations are of the sort that many find euphonic.

If you're more interested in the amp having a low signature and being faithful to the signal fed it, push-pull is a better choice. But you may not "like" the sound.

[tubewade]

As usual, SY has told it like it is. No one can tell you what you will like. Push pull may be less expensive and provide more power at the same time. But you may or may not like the sound.

Wade

[Jeb-D.]

Each amplifier sounds different, especially when no NFB is used. I've had good results with both SE and PP. There really seems to be equal pros and cons to each if you break it down.

But yes, SE iron is always bigger and about twice the price as an equivalent PP transformer. That is one of the con's of SE.

I think most people fear that since PP is more electrically correct than SE, that it will sound like your plain vanilla solid-state "blameless" amplifier. I have never found that to be true.

[limono]

I had a chance to hear a truly excellent PP amp using separate hige PSU's (80Lbs each ) and transmiting pentodes in the output stage. It was fantastic and the best I've heard -soft and brutal at the same time.
I think (thought ) that I like SE better but it's all aplication . If you use the same care and component quality in PP amp as in SET amps it should produce equally good results.
Good SET amps aren't euphonic nor warm. I'd say they tend to be fast ,unforgiving sometimes .
I built 45 Set and using Lowther DX4 in front horn crossed from 100 Hz up -104db (guess) . It barely makes it in moderate room with a little more demanding music. It sounds sweet but I think not very true.
In summary good PP amp is not going to be cheap (cheaper than SET)
Regards, L

[dsavitsk]

Originally posted by SY From an objective POV, single-ended amps perform far less accurately than push-pull.

True, perhaps, if you listen to sin waves, but I'm not sure this is quite as much of a fact as stated here. From Jack Elliano:

P-P will cancel even order harmonics but will add or emphasize the odd order. To illustrate this, one experiment that still intrigues me is when we took two audio frequencies and mixed them to one waveform which measured as 80% distortion. It then passed through a very good quality commercial P-P amp where the output waveform measured about 50% hmm! But when we then passed it through a SET amp and its output measured 80% just like the original. What Happened to the other 30% within the P-P amp? It appears that there are occasions that some audio signal complexities may also cancel or change structure from the original as well as the P-P tube transfer characteristics on even order harmonics.

[SY]

Well, if I were in the business of selling iron, I'd sure pimp for SE, too.

[limono]

they (electraprint) sell push -pull transformers too but SET crowd is willing to pay way more for the Iron (and parts ) than PP people .
I heard that in Japan there is no SET against PP dispute and both topologies are equally well regarded. Just those stupid "competetive " westerners always finding the line of conflict .

[Eli Duttman]

Originally posted by kacernator
Hi,

I have decided to build Mikaels Abdellahs SE KT88. But SE OPT are very expensive (I can get just Hammond 1628SEA). PP OPT are half the price of SE OPT.

I am going for the sound, but does SE has so much benefits that are worth the expensive OPTs?

My 2 cents. Build a PP amp that uses Mullard topology and a 6GK5 as the voltage gain tube and a 12AT7 as the LTP. The 12AT7/ECC81 is extremely well suited to PP amp service. The non-linearity of the 'T7 works to your advantage in a PP amp, as the NET harmonic distortion spectrum is an ear pleasing "waterfall", of 2nd > 3rd, > than 4th.

The high gm/low R_P small signal tubes I suggest give you excellent drive capability and resistance against slew limiting.