Fuzz bias problems

[shawnee]

Quick question guys: I have built several fuzz pedals now and have built them all with NPN's. (I have reversed the electrolytics and diode). When I bias the tranny's for 4.5v I only get about half that with the bias pot maxed out. This has happened on several fuzz face builds and now on a tonebender.

Right now on a Pastyface build, I am getting about 3.8v on the collector of Q1 and Q2 but can only get about 2.2v on the collector of Q3. I suppose if I used a 1M trim pot instead of the 500K it would get close to 4.5v but why? What the heck is going on?  I could understand on one build maybe, but all of them? What am I doing wrong here?

[Bret608]

That is an interesting question--does one type of polarity bias differently than another?

Have you found that the sound is affected at all? I'm thinking if the transistors aren't getting enough juice, it would sound spitty or gated. If it sounds good, you might not have a problem at all. I'm thinking JakeFuzz would have more useful things to say here.

One other thing to think about, and I only say this because I was confused the first time I looked at a trimpot. Do the 500k trimmers you used read "504" on them? If so, you're all set. If they say "503", you might have a 50k one in your build. Then again I doubt you would do that on several different builds! That'd be my department! 

[shawnee]

Thanks for the reply Bret. I got the Soulbender working now but I'm still not 100% sure what the problem is on the others. I have heard that germanium can bias differently than silicon so that may be part of the issue. I know I have tried to put germaniums into a silicon circuit more than once.