Still confused about transistor biasing!

[Joe Hart]

R.G. had told me that you bias transistors for the 3-knob ToneBender with the resistors connecting to the base of the transistors, but I'm still a little confused. I am using the "Color Sound Tone Bender" schematic on R.G.'s site, and there are two resistors (220K and 47K) connecting to Q1, a 10K connecting to Q2, and a 2M "fuzz" pot connecting to Q3. Do I use the 47K to ground to bias the first resistor? And the 10K to ground for the second one? And does the third transistor need biasing, or does the "fuzz" control mess with the bias to create the fuzz? Any suggestions where to use trimmers would be great, but with three knobs already, I don't want to spend a year twiddling things! In other words, where would trimmers make the biggest bang for the buck? THANKS!!
-Joe Hart

[petemoore]

I've spent about a year [if FF experiments count,ok] getting a Tonebender to work 'right'. The only thing I have to go by is sound clips and Zeppelin records...pretty good.
 Anyway the one I played just before raking leaves is the latest one, and it has bias pots soldered  in the perf for Q's 1,2 and 3 collectors.
 I believe I put a 4.7k resistor on Q1's "collector pot also to bump the 10k pots range from 0k-10k to 4.7k-14.7k ~ might have been Q2 but with that R a socket I can 'coarse tune' the range on the bias, then fine tune it from there with the bias pot.
 Starting with matched, tested Ge transistors goes a long way toward getting one of these ckt.s properly biased.
 Runoff groove has the voltage readings I used as a general guide for setting the biases, but in the end it's been set by ear, and I've been satisfied greatly for weeks now with it, I feel like I can finally leave a TB alone [ckt wise] and use it playing live as the 'main fuzz'!
 I found haveing the pots expecially for Q3 bias and to a lesser amt Q2 and lastly Q1 but I used all three.

[C Bradley]

Joe,

It appears to me that Q1 is the only transistor that you need at bias. Q2 is biased by Q1, and Q3 is biased by the diode connected to it's base.

A 33k resistor could be wired in series with a 25k pot, and then the whole thing would replace the 47k. With the 25k pot set at about 50%, you'd get close to 47k with a little adjustment up or down in bias voltage.  

Hope this helps,

Chris B