Big Muff PI clone sustain problem

[vinceg]

Hi, I built this pedal a few month ago and it worked well. Now, I notice that it has too much distortion with sustain pot at minimum and the sound seem dirty. What should I check?

This is schematic https://www.musikding.de/docs/musikding/muffram/muffv2schalt.pdf

[antonis]

Check for proper R6 connection between GND and Sustain Pot lug 1..
(R6 serves, except for minimum Sustain setting, as a "noise gate" for T2 gain stage..)

[vinceg]

I checked for R6 connection and it seem right

[antonis]

If so, check aroud R4/C4..
(T2 stage gain is roughly R9/R7 - for too much distortion, "something" severely dominates R7 value..)

Take resistance measuremet between Sustain pot middle lug and T2 Base..
Depending on test leads and C4 polarity, you should read open circuit when reading has settled down..

[vinceg]

Ok, I'll check it.

Also, I forgot to mention, that tone control is abnormal. It seems that when it is at a minimum the pedal has a greater volume. When I turn it clockwise, from about 9 o'clock, the volume decreases.

[antonis]

Check for R17 correct value and joint(s)..

Or better, post some pics of both sides of your PCB...