Adding a gain control to a Whisker Biscuit

[Captainobvious99]

First off-
Wow, its been about a month since I joined here and I already have a few pedals under my belt. I've done the beginner project NPN Boost, Shaka V, Zombie Chorus, and most recently the Whisker Biscuit. Its been quite a bit of fun and I'm learning alot as well thanks to Aron and all of the others here who contribute. Thank you all!

Now onto the question:

I love the sound, but I'd like to add a gain pot to the Whisker Biscuit to be able to dial back some of the gain for when you need just a touch of fuzz. Where would be the appropriate spot in the circuit to do this? Also, which potentiometer would make the most sense to use? Thank you in advance for the assistance.

Here is my layout. Note that I used 4 2N5088 trannys.

[slacker]

I'd try a pot wired like the dirt control in the Deluxe Bazz Fuss http://www.home-wrecker.com/bazz.html or add a "sustain" pot like in a real Big Muff.

[petemoore]

  A volume control could be at the input input gain control, try the volume on your guitar to see what this'd sound like.
  use a standard volume control wiring and call it a 'gain' knob spliced between any two stages, see Big Muff Pie knob called 'sustain'.
  Notice which WB stages resemble BMP gain/clipping stages, look for BMP mods that might apply.
  The input and output transistor share topology with big muff, the emiiter and collector resistor ratio play large role in setting the gain, also play a role in bias.
  Diddling with the emitter resistor value...smaller increases // larger resistance increases gain.  I like to start with 'big value' [?<1k...maybe 2k pot to decide what range might be suitable?] and trim it with parallel resistor [using a pot at first to find the gain desired from that stage].
  Since you have 100ohm resistors there, you can splice something in...series resistances add. A wire or wire with a switch in it could be used across either of series resistors to have switched resistances/gain there.
  The darlington stage could be messed with if 2 transistors were built to make darlington a 'pseudo darlington' stage.

 
 

[Captainobvious99]

Thanks for the suggestions. I'll start with the pot connected off of the darlington stage and see what that does for me.

I did fiddle with guitar volume controls but it doesnt offer quite as much control as I had hoped. Its not a huge deal as it still sounds very good, but I'll see what the added "dirt" pot will yield.