BIG MUFF PROBLEM

[Mike Burgundy]

Good going.
Here's what you want to see going through the circuit: you want the level to increase every gain stage, and with clippers you want to see, well, clipping. After every gain stage level can drop a little going through passives, and with the next gain stage it will increase again.
Now, let's have a virtual look at stage 1:
input = your regular signal (guitar, Ipod, looper, whatever input youre using). Q1 base is the same, perhaps a little less signal level. Q1 collector is a LOT louder, emitter just under Q1B. Then move on to the gain pot: top connection (almost) the same as Q1C, wiper same as that on 100%, less when rolling down. Q2B, Q2E (distortion!), now, *where* exactly does the excessive noise start? You've found the problem area, now you have to narrow it down. Measure/probe both sides of the coupling cap to stage 3 and carefully follow the schematic, taking note of your findings at every node of the circuit. Look at where the noise starts/is, look at the signal levels (any sudden drops/increase? Where would you expect a certain change, where do they actually happen?) , and everything that stands out. I'm guessing there's a short or dodgy connection there.

[Roger Martin]

I read somewhere, big muff is not working because of a wrong resistor value somewhere.
Have you checked them thoroughly ?