Sandspur fuzz sounds bad

[Chevy]

Just built the Sandspur fuzz, parts exactly as specified in the build documentation. Tried BC108's and 183's, both high and low gain versions, and even 2n797 Germanium transistors, and all different combinations of clean and bias settings.

Only thing that sounds ok is guitar turned down to 8 or 8.5 or so for that glassy bright tone with a little break up. when turned up to 9 or 10 on the Strat, the top end disappears and I get a sort of woolly dark distortion, not "clear" fuzz. I can't get a good fuzz sound at all. Strat is plugged straight into Sandspur, no buffer.

Wtf? What did I do wrong?

 

[JamieJ]

Have you biased the pedal? This is done by setting the voltage on Q2 collector (usually around to half supply voltage but adjust to taste) via the combination of trimmer and the external bias pot.

 

[swelchy]

adjust the clean pot all the way clockwise then adjust the bias to half supply voltage with multimeter...... then do small tweaks to the bias with fuzz knob cranked and volume cranked all the way up to taste.. that's how i set them up..

 

[swelchy]

oh.. and keep the "Sun" knob in the middle of it's range when setting the bias.. That way you get adjustment to the left and right when using the knob

 

[jwin615]

And no buffahs!

 

[Chevy]

revised...

Aye, Capt'n.... there be fuzz! Cool.

I do get a fuzz now, proper bias made all the difference, but seems there's a problem here... with supply V+ of about 10.4V, I can only dial in a minimum of 5.0V at the collector of Q2, with BOTH bias and sun pots cranked. Is this due to the transistors, or should the bias trimmer pot perhaps be like 10K?
That's with my 2N797 Ge NPN transistors in there. I would much prefer to be able to get this bias setting with the sun pot half way.

 

[JamieJ]

Is that Ge NPN or PNP? This is a NPN based circuit. If you have sockets in try the bc108s again. Be careful with Bc183s as they have a different pin out.

I’m hoping you can bias it correctly with the 108s in place. If you can’t double check your resistor values.

 

[Chevy]

Ge is NPN. Won't bias quite correctly with them, however, as per previous message. Put the 108's back in, and it does bias correctly.