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okhifi 25th August 2005 05:43 PM

is single end class a better than push - pull?
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is single end class a better than push - pull?

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leadbelly 25th August 2005 07:15 PM

Is Coke better than Pepsi?

rdf 25th August 2005 07:37 PM


Originally posted by leadbelly
Is Coke better than Pepsi?
In every way!

Miles Prower 25th August 2005 07:39 PM

is single end class a better than push - pull?

That's a big: "It depends".

Push-pull has certain advantages. It eliminates (or nearly so) the DC magnetizing current, and so makes the design and construction of output xfmrs easier. Balanced operation also eliminates (or nearly so) even order harmonics, making for cleaner output.

Unforch, it also removes the second harmonic, which doesn't seem to do much damage to listenability, and may even improve it. The odd-order harmonic content coming from a P-P stage has higher order harmonics (3, 5, 7, 9, etc.) even if the magnitude is lower, these have a greater affect on listenability. Can you control that with feedback? Sure, NBD.

Does it make a difference? Who knows? It all comes down to listenability, and that's strictly a personal preference. Some like P-P cleaned up with feedback; others prefer raw SE, and no feedback. You can fight about that one forever (and they're doing that over in the SS forum. :D )

mr mojo 25th August 2005 10:18 PM

I agree wholeheartedly about the coke/pepsi thing. In fact, I think a person's previous experiences, state of mind, sobriety level as well as speaker and room interactions will make far more difference than SE or PP.

To add to Miles' post: The center-tapped output xfrmrs of a PP amp, in addition to limiting/cancelling DC current and core saturation (allowing them to be simpler, smaller and cheaper)also cancels out some hum. Feedback in a PP amp will help decrease hum levels even further-with the combined action of the two allowing for less(cheaper) power-supply filtering such as C-R-C rather than using chokes-although there's certainly nothing wrong with using a choke in a PP power supply!

Without the combined action of feedback and center-tapped xfrmrs, hum can be a problem in a SET amp-but can be cured with care.

mr mojo

EC8010 25th August 2005 10:53 PM

No, no tolerance whatsoever...
Coke/Pepsi? We are talking about totally artificial hyped-up junk drinks made of water and artificial additives sold at an inflated price and consumed mostly by kids aren't we? Wouldn't a comparison between champagne and cava be more appropriate, or sauternes and graves? Something real... Please?

Johan Potgieter 26th August 2005 12:17 AM

I am always intrigued by this argument (was this opened mischievously?). In addition to factors mentioned by Miles and Mr Mojo:

Okhifi did not mention triodes specifically. A pentode will always have substantially more distortion (and very audible) than any p.p. circuit, going into high order harmonics. Then the removal of even order harmonics seems to be a stumbling block for some. One must see that correctly: It is not even harmonics per se that are removed, only even harmonic distortion, i.e. something added by the amplifier that should not have been there in the first place. (There is sometimes a perception that part of the original music is "removed".)

If looked at correctly, I for one cannot see that any circuit causing lower distortion, whatever the content, can be inferior to one causing higher distortion, when the original purpose is to have no distortion - that is not logical. (This with the proviso that one is aware of the listener fatigue caused by severe high order harmonics - I am excluding that for the moment.) Thus if a single ended triode is preferred because it has mainly 2nd harmonic distortion, then use a p.p. triode output stage; it will have even lower distortion, etc. Pentodes generally can be capable of generating some higher order products (they will do more so in single ended) but that depends on the design. However since the days of ultra-linear (rendering largely triode type distortion) I cannot see anyone using straight pentodes any more.

That is it, in a nutshell, for me. . .

arnoldc 26th August 2005 12:25 AM

very subjective... depends on whose ears :)

SY 26th August 2005 12:38 AM

Re: No, no tolerance whatsoever...

Originally posted by EC8010
We are talking about totally artificial hyped-up junk drinks made of water and artificial additives sold at an inflated price
SET in a nutshell.

Johan Potgieter 26th August 2005 12:46 AM

Dear oh dear SY!

NOW you are going to get an earfull! (But I will remember this retort - quite relevant.)


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