Fuzz Face/ Guitar Volume Pot Problem

[burntfingers]

Hi Guys,

I wonder if someone could help me. I have built a Fuzz Face clone which sounds great but the only issue is how it interacts with the guitar volume pot. It is only effective in the last tenth of pot travel, before that there is a big dip in output rather than the expected smooth decrease.

Does anyone know what causes this problem and how I can fix it? By the way I have also built a modified fuzz face/ Fulltone '69 that is fine, so it's a bit of a puzzle for me.

Thanks.

[BAARON]

What kind of transistors are you using?  And have you measured their hFE to see if they call into the ~80-120 sweet zone for a fuzz?  What you describe sounds a bit like what happens when you use extremely low gain transistors (hFE 30-40), as far as I can surmise from your description... it gets really anemic and thin sounding as soon as the volume is turned down on your guitar, eh?

[burntfingers]

I'm using AC128's. I have also tried NTE 127's with the same problem and I have used these transistors in similar circuits with good results.

The problem is my so much the tone thinning out as a noticable dip in volume when the guitar volume pot is reduced from maximum rather than gradual roll off.

Cheers.