germanium trans and bias stability

[Karmasound]

Would it be possible to make some sort of bias control for a fuzz face or germ tranny pedal that would lower or increase the bias automaticaly when it crossed a low or high threshold?



be nice to use some of those wacky ones laying around.



:?  :shock:

[brian wenz]

Hello Hello--
   An external pot [10 - 20K] wired to the collector  is the closest I've ever had!
Brian.

[Karmasound]

Do you mean instead of the 10k trimmer?


Use a pot outside instead?

Not sure if that would solve my problem or not. :?

[markusw]

Some time ago a played with trying to make a auto-biasing fuzz. The only thing I could get working was the smiley fuzz face, which has an external indicator LED for the Q2 C voltage plus an external trim pot. See http://diystompboxes.com/sboxforum/viewtopic.php?t=26074&start=0&postdays=0&postorder=asc&highlight=.

There is also a schemo for the Rockface which uses a a LDR instead of the biasing pot for Q2. In my hands however it never really worked. Although it does autobias, after playing a while Q2 voltage starts drifting. When I stopped playing it returned to V/2 after a while. I even tried to make a double-Rockface with 2 LDRs. See http://diystompboxes.com/sboxforum/viewtopic.php?t=27176&start=0&postdays=0&postorder=asc&highlight=

There are some other tricks like putting a Ge diode between B and E to compensate, which is supposed to work quite nicely. Futhermore, some other auto-biasing circuits have been discussed  while ago here in this forum.

Good luck,

Markus