Acoustic 360 fuzz (again) : fuzz vol. and gain both act as general volume

[eve-the-frog]

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 ?

[Ciaran Haslett]

I haven't looked at the schematic but it looks like both pots are grounded at at lug 1.  So when their wipers (lug 2) are fully CCW the next stage is grounded also.....so silent.

You would need to add a resistor between lug 1 and ground on the Gain pot so when you do turn it fully CCW thee is still some resistance to ground therefore not silent.  You'll have to test different resistor values to find one you're happy with.  Maybe start with 50K and see where that gets you.

I've no idea what that other resistor is in his build pic but it doesn't look like the method I described above anyway.

[eve-the-frog]

Thanks for your help.
I'll try that tomorrow...

If it could be the solution for stopping the pots to mute the sound when fully CCW, I guess it won't change the other behaviour of these pots : making anything but "master volume".
But I still don't fully understand how a pot works... So I may be totally wrong.

Anyway, I'll test it and come back to tell you what happens.

[eve-the-frog]

Question : do you want me to add a wire with a resistor between lug 1 and ground, leaving the existing wire in place ? Or should I just add a resistor between the existing wire and the lug 1 ?

[Ciaran Haslett]

Whatever is easiest so long as Lug 1 goes to one side of a resistor...and the other side of the resistor goes to ground.

[eve-the-frog]

I put 47k resistor on both lug 1.
Now the gain act clearly as a master volume (as it should be, I guess ?) but the fuzz volume also do the same, but with a very little volume increase from 0 to 10.

At this point what I think is removing the fuzz volume pot and keep this pedal with 4 knobs. But I think a pot is missing to precisely tweak my sound...
The blend pot is great but do not act like a fuzz amount pot.

The question is : how JohnK (and others who built this succesfully) have a correct fuzz volume and gain control...