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:  
  View Thread

starved plate

4/19/1999 11:19 PM
Donaldstarved plate
I'm working on a starved plate tube effect and have come across a weird bug in it. I can hear the volume increase as the tube (12AX7) warms up, but as soon as it gets warm, it dies. After a couple of minutes, it will fart if the strings are hit hard, and sustains a little more as time passes. After about five minutes, it works fine. Any ideas on what causes this?  
It is a 2 stage tube preamp running on ~40V B+. The only unusual thing is the fact that the grid is about two volts negative. I read somewhere that in starved plate designs, the electron cloud grows larger due to a less positive plate, so electrons cloud up around the grid causing negative grid current - I am assuming this is the reason for the negative grid. Is this bad for the guitar (running 2 volts across the pickups)? Is this causing my problem? Any help would be appreciated.

 
Replies:
Doc A grid bias of -2v is most likely p... -- 4/21/1999 7:25 AM
Jim L. You might want to run some sort of ... -- 5/12/1999 7:40 PM