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Old 30th October 2009, 12:44 AM   #1
DougL is offline DougL  United States
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Post Se Amp with Push Pull Transformer

I was reading "Designing Valve amplifiers" By Morgan Jones (Highly Recommended) and saw the page for cancellation using one valve, page 392.

I had some questions.
First, would each winding be 2*RP as a rule of thumb?
Would Av = 2 * mu/mu+1 ~ 1.8?

The circuit looks like it might work great with a toroid and maintain "perfect" balance. It would also work with something like the Lundahl LL1663, but not most classic push pull transformers.

I was thinking I could have a bit different amp.
Any thoughts are appreciated.

I was sketching concepts on my pad for this and thought I'd throw it out for comments.

Doug
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Last edited by DougL; 30th October 2009 at 12:44 AM. Reason: spelling
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Old 2nd November 2009, 07:37 PM   #2
Elias is offline Elias  Finland
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Hello,

got any picture of the concept?


- Elias
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Old 2nd November 2009, 07:40 PM   #3
DougL is offline DougL  United States
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I will Sketch one up today.
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Old 2nd November 2009, 08:31 PM   #4
45 is offline 45  Italy
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Quote:
Originally Posted by DougL View Post
I was reading "Designing Valve amplifiers" By Morgan Jones (Highly Recommended) and saw the page for cancellation using one valve, page 392.

I had some questions.
First, would each winding be 2*RP as a rule of thumb?
Would Av = 2 * mu/mu+1 ~ 1.8?

The circuit looks like it might work great with a toroid and maintain "perfect" balance. It would also work with something like the Lundahl LL1663, but not most classic push pull transformers.

I was thinking I could have a bit different amp.
Any thoughts are appreciated.

I was sketching concepts on my pad for this and thought I'd throw it out for comments.

Doug

I think it could work well with triodes like the 6080/6AS7 that have a very low mu anyway....

Cheers,
45
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Old 2nd November 2009, 08:42 PM   #5
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It seems like such a nice concept. However, the problem is that the AC signals will exactly cancel each other out leaving you with almost exactly no output. That is, it is an error in the book.

Sims are from Slagle from a while back. Also, if you search AA for "chokertina" there was a discussion on this in 2003.
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Old 2nd November 2009, 09:17 PM   #6
45 is offline 45  Italy
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I was thinking about something like the Klimo Beltaine. Using the 6AS7, one triode is the amplier and the other for the DC balance only. Cathode follower config. if you like. Probably it doesn't work as well because the DC side has to be a current source.
I don't have the book by Morgan Jones .

Cheers,
45

Last edited by 45; 2nd November 2009 at 09:36 PM.
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Old 2nd November 2009, 10:30 PM   #7
DougL is offline DougL  United States
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Here is The Concept.

Push pull transformer with split, not center tap primary.
Standing current cancels. And since there is only 1 tube and Icathode and IPlate are equal until A2, the current ballance should be "perfect".

Morgan Jones said it was a problem to drive.

Doug
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Old 2nd November 2009, 10:32 PM   #8
DougL is offline DougL  United States
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Quote:
Originally Posted by dsavitsk View Post
It seems like such a nice concept. However, the problem is that the AC signals will exactly cancel each other out leaving you with almost exactly no output. That is, it is an error in the book.

Sims are from Slagle from a while back. Also, if you search AA for "chokertina" there was a discussion on this in 2003.
Really?

Thanks.

Sounded too good to be true.

Doug
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Old 3rd November 2009, 12:07 AM   #9
Matt BH is offline Matt BH  United Kingdom
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It should work. The ac signals at the anode and cathode are opposite phase right?
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Old 3rd November 2009, 12:20 AM   #10
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"The ac signals at the anode and cathode are opposite phase right?"

Yes, but they are then connected to the same phase connections on the xfmr where they then cancel out.


Some related ideas here:

DC compensated SE output transformer
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