Output Transformer Air Gap

sousmielie · 25th July 2008, 10:22 AM

Hi all,

I have a quick question. Is it neccesary to have a air gap in a output transformer for a pp amp? I can understand the use of the air gap in se amps, but I've been browsing some sites and some say pp should have it and some say it shouldn't.

I haven't built pp valve amps before only se.

Thanks,
Mielie

SY · 25th July 2008, 11:05 AM

Quote:

Is it neccesary to have a air gap in a output transformer for a pp amp?

No. If balanced properly (an easy thing to do), the DC from each half of the push-pull pair cancels the DC from the other half. That's why PP transformers are smaller and usually have less leakage inductance for a given level of care in construction.

analog_sa · 25th July 2008, 11:11 AM

Quote:

Originally posted by sousmielie

I have a quick question.

And here is a quick answer before the guys with the long formulas have responded.

The airgap will improve linearity and allow for some unbalanced dc if the tubes are not well matched. Too much gap will decrease primary inductance.

Practically all cores have some distributed gap. I have an old WE pp transformer which does not have a defined gap but all Es are on one side and all Is on the other. The core is indeed huge but it will take 60mA unbalanced without saturation.

sousmielie · 25th July 2008, 11:28 AM

Thanks, that's what i thought

25th July 2008, 10:22 AM	#1
sousmielie diyAudio Member Join Date: May 2005 Location: GP (Gangstas Paradise)	Output Transformer Air Gap Hi all, I have a quick question. Is it neccesary to have a air gap in a output transformer for a pp amp? I can understand the use of the air gap in se amps, but I've been browsing some sites and some say pp should have it and some say it shouldn't. I haven't built pp valve amps before only se. Thanks, Mielie __________________ It's one of the best feelings in the world when you build something without it going up in smoke............

25th July 2008, 11:28 AM	#4
sousmielie diyAudio Member Join Date: May 2005 Location: GP (Gangstas Paradise)	Thanks, that's what i thought __________________ It's one of the best feelings in the world when you build something without it going up in smoke............

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