Ultrapath output transformers

[bequerel]

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.)

[Bas Horneman]

What about the ultrapath configuration.

You can use any transformers for ultrapath. Gapped or Parafeed doesn't matter.

[dsavitsk]

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.

[bequerel]

Thank you guys!
The transformers I have are standard ("gapped"?), so I understand that they should be fine.

[DougL]

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.

Regards;

Doug

[arnoldc]

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?

[dsavitsk]

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


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.

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

[DougL]

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


Regards

Doug

[Bas Horneman]

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

[arnoldc]

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.