That's correct, It had been reported that it had too much volume with 12K so the value was changed by request!
Tremolo is another circuit that suffers this dilemma so it's always good to see a Volume control or Trimmer on the PCB!!!!
R34 & R35 - 47K effect Volume. This is a common issue depending on what you perceive as a drop in Volume.
You could try stacking 47K on both R34 & R35 resistors temporary & that will give you 23.5K & see if you like that.
You can bring them down to 10K if you want to try that.
You can use a SPDT ON/OFF/ON for the Shift Toggle instead of ON/ON & add a 10 or 15nF capacitor to give you an in between shift so you have 3 instead of 2 positions!
It requires just soldering the cap between bottom Toggle pad & Leg 1 of Tone pot like I did
Mine is on the Solder side of the PCB :
This is my own Eyelet Board Construction & is 2 similar circuits combined with a Jfet buffer on the Input by Chuck D. Bones.
The toggle switches between Silicon, None & Germanium/ Silicon Diodes!
It goes from Clean to Mean with the Drive knob which is basically a Bias pot.
Chuck can explain on...