Twin Face Bias issue

[Drlufk00]

This may be a strange question… I am in the process of building a fuzz pedal (Twin Face) and am trying to bias the transistors.

First issue is that in the past I have grounded the black lead of my multi meter to the enclosure, on this build if I do that I get a reading of 0. The red lead is on the emitter of Q2. If I move the black lead to the ground tab of the input jack I get a reading. Why would this be? This is a powder coated enclosure from Tayda if that makes a difference… is this ok? Will I have terrible noise if the enclosure isn’t acting as a ground?

Second issue is that the voltage I get from the NPN side is negative and from the PNP side is positive. It seems it should be reversed from what I have read? I have built one other fuzz face and it was an NPN and my voltage at Q2 was negative as well… that pedal works well but is noisy. Am I reading wrong or is this backwards? How could I fix it if it’s an issue I need to address?

Last issue is that the best bias I can get on the NPN side is -3.6v. Would changing the 10k trimmer pot out for 20k give me enough travel to achieve proper bias voltage of (-)4.5v?The PNP side biased well, but I have that one on an external 10k rotary pot.

 

[Fama]

First issue is that in the past I have grounded the black lead of my multi meter to the enclosure, on this build if I do that I get a reading of 0. The red lead is on the emitter of Q2. If I move the black lead to the ground tab of the input jack I get a reading. Why would this be? This is a powder coated enclosure from Tayda if that makes a difference… is this ok? Will I have terrible noise if the enclosure isn’t acting as a ground?

It sounds like your jacks are not making contact with the enclosure. It's common practice to remove the powder coating from those holes to ensure the jacks make contact - sandpaper might work fine, I use an old knife personally, I'm sure there are other good tools too.

I'm not sure about terrible noise, but more noisy for sure.

If you ask me, the voltage is fine, plus you said it worked the same way in the other pedal you built, so I wouldn't worry about it. Sorry I can't answer the bias trimmer question. How does the pedal sound?