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Post by swampcooler on Jul 29, 2007 11:56:51 GMT -7
Hi,
I'm trying to get my KT-45 to run cathode biased. Here's what I have done so far:
I have disconnected the grid/pin 5 bias voltage on both tubes and grounded the resistors of both pins 5. What do I do with the now unused bias supply wires?
Pin 1, suppressors, goes to ground.
I have taken both cathodes at pins 8, connected them and then sent them to ground through a 470 ohm 10 watt resistor, with a 47 mfd bypass cap. My current draw is now 35.5 ma with 404 volts on the plates. It should be operating, I think . . . ?
I have no sound at all, not even when I check voltages with my meter around the tube pins - no scratches or any hiss, nothing. When I wire it back to fixed bias, it still works fine.
Any thoughts on this? I would really like to make this work for me and my amp.
Thanks for your replies, Swampcooler
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Post by dixiechicken on Aug 1, 2007 7:55:03 GMT -7
Out of curiosity - why do you wanna do that? Something you'd hope to gain? If you dont know exactly what you're doing - it sounds a bit risky to me. I have the impression Doc really considers the overall layout and parts in any amp he designs. You probably risk the sound Doc was after when he designed the KT-45. If I were you, I would sell it and get one of Doc:s EL84 amps instead - they are all cathode biased I think. ( maybe you already have one? ) Cheers: Dixiechicken
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