powering up a Dallas Arbiter fuzz face with ac128 PNP

[arma61]

Hi, a stupid question ! to power up a Dallas Arbiter fuzz face with ac128 PNP with  negative ground did I need only to swap the battery poles?, I mean is the "black pole" of the battery -9V or just 0 ? thx for help

[bobster]

swap battery poles and electrolytic capacitor poles and u should b ok

[R.G.]

My advice, based on decades of electronics experience in general and years of experience with this conversion in specific is:

Do not do this.

I keep having to help people fix their fuzz face and other PNP germanium effects that they have decided to power from negative ground instead of positive ground. In many cases it works. In other cases, there is no fix I can find that will make it work except reversing the power supply back to positive ground.

Changing from a positive ground to negative ground is NOT a simple, easy thing to do.

I get tired of typing this. Search the archives for notes I authored on negative ground PNP effects.

[darron]

hey. i don't want to go against R.G. on this. there's a schematic and layout for both negative and positive ground here. http://www.tonepad.com/project.asp?id=38

if you make it negative ground though the transistors will oscillate and cause a motorboating effect when you turn the gain up. pretty much unusable. you can get rid of this by installing a 1000uf capacitor going across the positive and negative terminals. have it onboard if you can as further away will have less effect. but why would you build something only to make compensations? i guess for the convenience of a negative grounded pedal...

it's one of the simplest projects, but it can cause a lot of pain in terms of grounding, biasing and leaky germanium transistors

[bumblebee]

I just built one - ground,it was okay if you like a heap of oscillation,but i rewired it + ground and its way better.
Neg ground FF doesn't have much use really,it kinda sucks!

My advice is +  ground!

[arma61]

thx to all, I've already build it, and when testing I didn't like its sound, so I get the doubt about the swap of +&-. I know that positive ground is a pain, also you cannot put the FX box in a chain with the same power supply!, so it must be powered alone.
I got another doubt this morning, I got the 2 AC128 from Banzaieffects, they've "selected" them in pair, I've noticed this morning that on one there is one black stripe and on the other one there are 2 black stripes, I'm gonna check on monday with them if that means q1 (1 stripe) and q2 (2 stripes) or may be somebody here knows that.