Push Pull Output tranies for SE amp?

targeteye · 19th August 2008, 02:33 AM

Hello all.
I managed to pickup a set of Fisher KX-200 Iron. I have no desire to build a Push Pull amp but would like to build a SE amp.

Would these transformers be a candidate to build a 45 or 71a .7 to 2 Watt SE amp with these? Or should I not waste my time an just wait till I can get some real SE output transformers?

Thanks
Steve

wrenchone · 19th August 2008, 03:06 AM

Don't waste your time with the Fisher P-P for SE purposes, as they most likely aren't properly gapped to deal with DC. At the power level you mentioned, you can get a nice piece of iron for $20 or so from Edcor. Save the Fisher transformers for when you get interested in a P-P design, or sell them on Ebay to get the bucks for the Edcor transformers. The smaller Hammond 125 series single-ended transformers would also be a good starting point.

Jeb-D. · 19th August 2008, 05:39 AM

You can use them as a parallel feed type single ended, but not a conventional single ended.

Quote:

Or should I not waste my time an just wait till I can get some real SE output transformers

Or you could not waste your time with single-ended and use the transformers you have.

plovati · 19th August 2008, 07:09 AM

You can always use the Klimo Beltaine solution: one primary winding of the PP active, the other used for DC compensation by means of a current sink (EL34 in the case of Klimo).
Note that in the this case the primary impedance is a quarter of the original anode to anode primary impedance, it is possible to play a little bit with the 4-8 ohm secondary to adjust it.

fredex · 19th August 2008, 11:11 AM

Quote:

Originally posted by targeteye
Hello all.
I managed to pickup a set of Fisher KX-200 Iron. I have no desire to build a Push Pull amp but would like to build a SE amp.

Would these transformers be a candidate to build a 45 or 71a .7 to 2 Watt SE amp with these? Or should I not waste my time an just wait till I can get some real SE output transformers?

Thanks
Steve

Although not 'technically' correct don't listen to those who have not tried it. I and others I know have, and it usually works fine. Partridge recommended an air gap for PP transformers as well for technical reasons. If the SE sound rocks your boat you can buy SE tranys later, get that iron heated!
Cheers

JandG · 19th August 2008, 01:22 PM

Yes, I have a SE amp running old Pilot PP iron & it is way fine, don't know how, but it is, No special circuit. PSE configuraton 6sn7/6sn7

targeteye · 20th August 2008, 04:16 AM

Thanks folks. Got the 45's got the trannies, got a bench supply. Guess I'll just hook it all up and give a listen.

Balancing out the dc on the other 1/2 of the Transformer is an interesting idea!

Steve

fredex · 20th August 2008, 05:51 AM

Quote:

Originally posted by targeteye
..............Balancing out the dc on the other 1/2 of the Transformer is an interesting idea!
Steve

You must do this through a high impedance source. Both halves of the primary are tightly coupled, a low impedance across one half will shunt the signal in the other. If you use the whole primary in series you will get more inductance = bass that goes lower.

19th August 2008, 02:33 AM	#1
targeteye diyAudio Member Join Date: Apr 2007	Push Pull Output tranies for SE amp? Hello all. I managed to pickup a set of Fisher KX-200 Iron. I have no desire to build a Push Pull amp but would like to build a SE amp. Would these transformers be a candidate to build a 45 or 71a .7 to 2 Watt SE amp with these? Or should I not waste my time an just wait till I can get some real SE output transformers? Thanks Steve

19th August 2008, 07:09 AM	#4
plovati diyAudio Member Join Date: Mar 2005 Location: near Milan	You can always use the Klimo Beltaine solution: one primary winding of the PP active, the other used for DC compensation by means of a current sink (EL34 in the case of Klimo). Note that in the this case the primary impedance is a quarter of the original anode to anode primary impedance, it is possible to play a little bit with the 4-8 ohm secondary to adjust it. __________________ Piergiorgio

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19th August 2008, 03:06 AM	#2
wrenchone diyAudio Member Join Date: Feb 2004 Location: Silicon Valley	Don't waste your time with the Fisher P-P for SE purposes, as they most likely aren't properly gapped to deal with DC. At the power level you mentioned, you can get a nice piece of iron for $20 or so from Edcor. Save the Fisher transformers for when you get interested in a P-P design, or sell them on Ebay to get the bucks for the Edcor transformers. The smaller Hammond 125 series single-ended transformers would also be a good starting point.

19th August 2008, 01:22 PM	#6
JandG diyAudio Member Join Date: Jan 2005 Location: Washington State	Yes, I have a SE amp running old Pilot PP iron & it is way fine, don't know how, but it is, No special circuit. PSE configuraton 6sn7/6sn7

20th August 2008, 04:16 AM	#7
targeteye diyAudio Member Join Date: Apr 2007	Thanks folks. Got the 45's got the trannies, got a bench supply. Guess I'll just hook it all up and give a listen. Balancing out the dc on the other 1/2 of the Transformer is an interesting idea! Steve

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