Tube Phono Preamp Help

[johnkpap]

Hi can someone help me?

I have built the following Phono preamp from the Bonavolta site


http://www.bonavolta.ch/hobby/en/audio/dyn_upas.htm


I have checked every thing it all looks fine I have about 210 volts on the anodes All parts were bought new Except the transfomer and 680uf 450v cap in the PSU.

When I connect it in place of the El-cheap-o $20.00 preamp my Pioneer AV amp Puts out nothing !!!! I suspect it is shutting down because it dosn't like my preamp.

What do I need to do to get the Tube Pre Amp to work with my Pioneer AV amp?

Would a 220k resistor across the output Help?

I havent built a Valve Amp since I was a Apprentice 20 years ago so I have
forgoten alot of my training on tubes.

Kindest Regards

Johnkpap

Electronics Tech

 

[johnkpap]

Hi Everyone,

I found the Problem!!!! the 1uf caps in the output stage were BAD !!! 3of the 4 had died I suspect that they are a bad batch or the 400v rating was not what was printed on them.

You cant Even trust new Parts !!!!

The CCT works very well I have a little hum which should go away
once everything is shielded.

Johnkpap

Electronics Tech