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Old 23rd October 2006, 04:55 PM   #1
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Default Ultrapath output transformers

I know that the parafeed configuration calls for special requirements regarding the construction of the output transformers used in eg. a linestage. What about the ultrapath configuration. Can I use the same transformers as I would have done in a "standard" configuration? (We are talking linestage here.)
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Old 23rd October 2006, 04:57 PM   #2
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Quote:
What about the ultrapath configuration.
You can use any transformers for ultrapath. Gapped or Parafeed doesn't matter.
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Old 23rd October 2006, 05:02 PM   #3
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Originally posted by Bas Horneman
You can use any transformers for ultrapath. Gapped or Parafeed doesn't matter.
No, you can't use parafeed transformers. There is DC on them.
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Old 23rd October 2006, 05:07 PM   #4
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Thank you guys!
The transformers I have are standard ("gapped"?), so I understand that they should be fine.
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Old 24th October 2006, 04:16 AM   #5
DougL is offline DougL  United States
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No, you can't use parafeed transformers. There is DC on them.
My understanding is that "Parafeed" transformers are not designed to have DC current across their primary.
There should be no issue using them in an ultrapath circuit, because the cap on the cathode leg of the transformer blocks DC current from plate to cathode.
Since there is no DC current, transformers with less air gap and a smaller cores can be used.

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Old 24th October 2006, 04:40 AM   #6
arnoldc is offline arnoldc  Philippines
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I have not tried parafeed myself and this is something I'd like to explore. I have a spud amp made of a single 417A which is wired normally. As I am having small OPTs made, I am hoping of getting better performance if I wire the amp in parafeed.

So the next question is, what sort of capacitor one should use for parafeed? I understand it has to be relatively high in value, i.e., 5uF or something and must be non-polar. Is this really the case?
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Old 24th October 2006, 05:12 AM   #7
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Quote:
Originally posted by DougL

My understanding is that "Parafeed" transformers are not designed to have DC current across their primary.
There should be no issue using them in an ultrapath circuit, because the cap on the cathode leg of the transformer blocks DC current from plate to cathode.
Since there is no DC current, transformers with less air gap and a smaller cores can be used.
No, you are wrong. The ultrapath is a single feed design.

Here's the schematic

Click the image to open in full size.
shamelessly taken from http://www.nutshellhifi.com/library/ETF.html

If there is no DC through the transformer, then there is no DC through the tube either.


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Originally posted by arnoldc
So the next question is, what sort of capacitor one should use for parafeed? I understand it has to be relatively high in value, i.e., 5uF or something and must be non-polar. Is this really the case?
There is aparently a bit of black magic involved, but that magic depends on the plate load. If you use a choke load, then there is some math you can do, but with a CCS it is little more guess work. But, 5uF is usually a good starting point (Here's where I asked the same question, I am drsx over there): http://www.audioasylum.com/forums/ma...ages/5502.html
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Old 24th October 2006, 03:57 PM   #8
DougL is offline DougL  United States
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No, you are wrong. The ultrapath is a single feed design
Agreed.

I confused it with what Lynn is calling the Western Electric (output), which does not have DC current.

http://www.nutshellhifi.com/library/Pix-D.gif


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Old 24th October 2006, 04:49 PM   #9
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A parafeed transformer always needs a dc blocking cap. But I don't see why you could not use ultrapath as well. Ultrapath is from b+ to cathode as in Jeff Lessard's Horus.

http://www.magnequest.com/diy/lessar..._schematic.htm
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Old 25th October 2006, 12:38 AM   #10
arnoldc is offline arnoldc  Philippines
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Quote:
There is aparently a bit of black magic involved, but that magic depends on the plate load. If you use a choke load, then there is some math you can do, but with a CCS it is little more guess work. But, 5uF is usually a good starting point (Here's where I asked the same question, I am drsx over there): http://www.audioasylum.com/forums/m...sages/5502.html
Thanks for the link. It was a good read.
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