Transformer Specs ???

[rlyach]

I recently ordered a Stereomour kit and Eileen was kind enough to send me the manual while I wait for my kit (I am having a hard time waiting). I am an electrical engineer and have built a couple of tube guitar amps so I am somewhat familiar with tube circuits and design. I went through the manual and schematics and I have been able to find everything except the specs for the transformers. Does anyone know where I can get the spec sheets for the transformers / chokes? I am thinking of upgrades and possible covers for the chokes.

Thanks,

 

[Paul Birkeland]

Hello Randy,

Which specs in particular are you interested in?

-PB

 

[rlyach]

I was looking to verify the pin-out of the output transformers. I think I have figured it out based on the connection options in the manual. If my assumptions are correct, there should be a way to wire them for 6 ohms (short 6 and 3, short 1 and 8, outputs on 8 and 7). Also I wanted to see the wattage and current ratings on the transformers.

Thanks

 

[Paul Joppa]

I've never documented the winding details for the output transformer OT-2; it's kind of confusing and I consider it proprietary as well. I have however documented the connections. There is no way to get a 6-ohm secondary, but a 12-ohm connection is possible (when used at a nominal 4K primary impedance). If you send me an email address through the Forum PM facility, I'll send you the PDF.

The transformer is designed to take 140vRMS at 25Hz without saturation. That's 4 watts at 4K primary impedance, or 2 watts at 8K (as used in the SEX amp v.2.1). Some designers would push that to 170v - the transition into saturation is kind of amorphous - but 140v is my spec.

It is not designed to take any DC current; in my measurements it was able to take 2.5mA. But this was just one sample; it's not a spec I would count on.

 

[rlyach]

Thank you so much for the information. After reading your post, the light turned on. I have never worked with a parafeed design before, only direct drive, and the transformer specs are quite a bit different between the two. That explains a lot. I will send an email for the pdf. Thanks again for the post.