I call myself the buggy guy...
In my previous post I talked about boxing issue. Now it's OK.
But later I discovered that Fuzz Vol. and Gain pots both act exactly the same : a master volume for the entire FX. The sound is exactly the same in whatever position, except the loudness of the sound of course.
I tried another layout from JohnK (acoustic 360 fuzz with tilt and blend) with exactly the same problem.
Here is the layout I used :
Other than that it works great.
Another guy had the same issue. He reports in the comments of the posted layout, and John's answer was "it definitely shouldn't be acting like that at all. you must have an error somewhere (solder bridge/misplaced component/wrong value component etc.)"
But I build this one from two different layout, with different components and it is exactly the same...
If John is around I'd really appreciate his comments.
And I have another question. In the picture of John's built I can see a resistor that's not on the layout : the vertical one in the left center part of the board. Could it be the answer ?