ampage
Tube Amps / Music Electronics
For current discussions, please visit Music Electronics Forum. New: view Recent Searches.
New: visit Schematic Hell!
The sunn still shines online!

 
Listen to great tunes streaming live right now!

ampage archive

Vintage threads from the first ten years

Search for:  Mode:  
previous: Jim Jones Hi guys,I know ther... -- 9/13/2000 5:08 PM View Thread

Re: Small sig. pentodes - EF86 (Long)

9/14/2000 12:05 AM
nuke
email
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.

 
Replies:
Jim Jones Hi Nuke,Thanks for ... -- 9/14/2000 2:56 PM