Tube DIY Asylum

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RE: how to remove feedback loops

Posted by Stuben on June 12, 2017 at 14:25:05:
Vinnie,

Remove the feedback loop, put a nice solid voltage on G2, run your cathodes through the opt secondaries to ground for cathode feedback, you still need the resistance up or down stream of your OPT secondaries. Use a good output transformer I've used 5K for my stuff both PPP and SET. The point about a 10K primary is valid, it should help in your quest for lower distortion with no GFB. You will have the bias voltage across your speaker terminals, for these easy to drive Pentodes, it's not a big deal.
Give it a try. I found my build to sound better in PPP than strapping for triodes, if this were a SE application it would be a different story. I used the LL1682 OPT PP with a 5 ohm secondary.

Stuben