Joe Davisson Easy Drive questions

[mordechai]

1.  What would varying the 68K resistor to the 9V power source do to the circuit?  Introduce/reduce noise?  Alter tone?

2. I tried following the suggestion to use a 1K pot in the place of the 680Ohm fixed resistor as a drive control.  I tied lug 3 to the top point of the fixed resistor spot, lug 1 went to ground, and lug 2 went to the capacitor-to-ground.  However, I was not able to vary the drive, it remained fixed.  Anyone have a sense of what I did wrong here?

[Govmnt_Lacky]

2. I tried following the suggestion to use a 1K pot in the place of the 680Ohm fixed resistor as a drive control.  I tied lug 3 to the top point of the fixed resistor spot, lug 1 went to ground, and lug 2 went to the capacitor-to-ground.  However, I was not able to vary the drive, it remained fixed.  Anyone have a sense of what I did wrong here?

If you are just REPLACING the 680ohm resistor with the 1K pot, then I believe you wired it incorrectly. Simply connect one pad (from the removed 680ohm resistor) to lugs 1 &2. Then tie the other pad to lug 3. I believe this is the correct way to wire a pot as a variable resistor. I think the way that YOU wired it was like a voltage divider.

Good Luck 

P.S. If turning the pot does not respond properly, then switch the wires around!

[allesz]

Hallo mordecai.
I love simple overdive and boosters like the easydrive... electra... bazz fuss etc. (probably because I am not good enough for bigger projects and IC
I agree with Govmnt_Lacky about wiring the "gain" pot as a variable resistor: the center lug of the pot must be connected to one of the outside lugs; now you have a pot with just two lugs; connect one of this lug to the emitter of the transistor and the other one goes on earth. The cap must stay connected between emitter and ground by itself.
About the 68K resistance that goes from the battery + to the collector of the transistor... changing it will result in (beware I am quite ignorant about electronic theory, this answer is stolen from something that Hemmo P. (mr. bazz fuss) wrote long time ago) more distortion if you go higher (like 100k or 150k) and more output, but less distortion, if you go lower (like 33k or 10k...).
The emitter resistance in a good place to experiment, but remember that if you keep in place the cap on the emitter you can't go to zero resistance (it will stop working) so put a small resistor (100 Ohm will be just sufficient) between the pot and ground.
My advice is... destroy everything and swap every part, you will have a lot of fun. Then go back to the standard project  .

[mordechai]

This is really helpful, thanks so much!  it is a terrific sounding overdrive, every bit as organic and "tube-y" as any other OD I've tried.