Tube Amps / Music Electronics
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|9/14/2000 12:05 AM|
|nuke||Re: Small sig. pentodes - EF86 (Long)|
I think you could tweek a few things, that's a tremendous amount of gain for a guitar input circuit to have. I doubt if the voltages you are seeing are meaningful. Make sure the control grid is grounded by by some means of a load resistor. You could also lower the bias by increasing the cathode resistor if you like.
One way you can tame the EF86 is by lowering the screen voltage. Rather than a 1 meg to the Vp, try using a divider network to get say 1/2 Vp to the screen. Try adding a 1 meg to ground at the pin 1 and 1 meg screen supply resistor.
I'd also stick with metal films on the cathode and plate resistors to help control noise. Perhaps a ceramic socket too. Some kind of grid stopper on the input might be advisable as well.
|Jim Jones Hi Nuke,|