How to gap output transformers?

quikie22 · 5th May 2011, 12:46 PM

I have 2 cheapie OPTs. They are non-gapped and thus prone to saturation st higher powers. I plan to take apart the laminations and gap it. Anyway to calculate the ideal gap distance? Any particular material I should use? A friend has suggested using simple 70gsm paper. Any thoughts?

Alastair E · 5th May 2011, 02:36 PM

Assuming SE trans......

No point in gapping p-p to my knowledge, you'll just lose inductance when you do...

Even a cheapo SE trans will be gapped--even those in old radios and TV sets Ive seen were gapped...

Gap on average is 0.2mm--Good starting point, Measure, tweak and measure again.....

So--That mans you need a 0.1mm thick material. (mag gap is double the thickness of material--crosses gap twice....)

quikie22 · 5th May 2011, 06:08 PM

you are right.. SE trans

these are real cheapies around 4GBP ea. E-I core with alternating E-I laminations. NO GAP for sure. maybe around 5-10W max.

While waiting for answer decided to try it out by unlaminating the core and rearranging the E and the I. Tried a with 80gsm A4 paper and also dot matrix printer paper (thin type, feels thinner than 70gsm paper) to gap the Es and the Is.

Findings are 80gsm paper is too thick, loss of bass. changed to the thinner paper, sounds better than ungapped, but am sure things can be improved.

Any other suggestions of materials I can try? Does it make a difference wht material is used?

5th May 2011, 12:46 PM	#1
quikie22 diyAudio Member Join Date: Sep 2009	How to gap output transformers? I have 2 cheapie OPTs. They are non-gapped and thus prone to saturation st higher powers. I plan to take apart the laminations and gap it. Anyway to calculate the ideal gap distance? Any particular material I should use? A friend has suggested using simple 70gsm paper. Any thoughts?

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5th May 2011, 02:36 PM	#2
Alastair E diyAudio Member Join Date: Feb 2004 Location: South Wales	Assuming SE trans...... No point in gapping p-p to my knowledge, you'll just lose inductance when you do... Even a cheapo SE trans will be gapped--even those in old radios and TV sets Ive seen were gapped... Gap on average is 0.2mm--Good starting point, Measure, tweak and measure again..... So--That mans you need a 0.1mm thick material. (mag gap is double the thickness of material--crosses gap twice....)

5th May 2011, 06:08 PM	#3
quikie22 diyAudio Member Join Date: Sep 2009	you are right.. SE trans these are real cheapies around 4GBP ea. E-I core with alternating E-I laminations. NO GAP for sure. maybe around 5-10W max. While waiting for answer decided to try it out by unlaminating the core and rearranging the E and the I. Tried a with 80gsm A4 paper and also dot matrix printer paper (thin type, feels thinner than 70gsm paper) to gap the Es and the Is. Findings are 80gsm paper is too thick, loss of bass. changed to the thinner paper, sounds better than ungapped, but am sure things can be improved. Any other suggestions of materials I can try? Does it make a difference wht material is used?

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