Need help, converting an PNP fuzz to work with Powersupply

[sha33]

Hi everyone,

I am a bit lost between PNP, NPN, positive and negative ground. I read several topics, but no one answers my question. So here i go: I want o build a 60's style Fuzz Fzce, with Germanium trannies.
Here is the build schematic :



Now, what do i have to do as i would like to daisy chain this pedal wih my others, and keep germanium trannies. So should i use NPN tranies and/or flips the caps and/or flip the power wires (+9v/-).. I am kind of lost..
Any recommandations about wich trannies to Use ? AC128 (PNP) or AC187 (NPN)

Thank you very much,

Nicolas

[slacker]

The easiest thing to do is use NPN transistors and switch it to negative ground by flipping the power wires -9V becomes +9V +ve ground becomes -ve ground also flip the two polarised caps, the blues ones. That will definitely work with a power supply daisy chained with other negative ground pedals.
You can use PNP transistors and convert the circuit to negative ground but this doesn't always work, you can get problems with noise a the circuit can oscillate.

Welcome aboard

[sha33]

Thank you for your answer ! so flip the electro caps, flip the power wires, and go with a NPN. If i want to test with a PNP, i flip everything and just install the PNP instead on the NPN?

[induction]

It is true that switching to NPN transistors is probably easiest, but you mentioned "60's style", so maybe you want it to sound vintage? The transistors themselves have an impact on the sound of the pedal, and your options for NPN Ge's might be kind of limited. Lots of people like to swap transistors until they find the magic, so the availability of the transistors can cause difficulties with the NPN option.

An alternative idea is to install a voltage inverter. That way you can use a daisy chain for power with PNP's.

It's just another option, though. Slacker's advice is also good. Your decision depends on your priorities and preferences.

Read this, if you haven't yet.

[sha33]

induction, the voltage inverter option is genious !    So i can have my Fuzz-face the way it was meant to be, and just power it up with my PSU. Should i use plastic jacks to isolate them from the metal enclosure?

[induction]

The input/output jacks don't need to be isolated, but the DC jack does.

[Transmogrifox]

You can build the inverter into the box with the fuzz and then you don't have to do anything special with the DC jacks.

I always feel like the conversion of a PNP circuit to negative ground shouldn't be a problem, but practical applications shows there is more than meets the eye.

In a world of ideal capacitors this wouldn't be a problem, but alas, instability crops up through all of the non-ideal things not visible in a schematic.  Maybe one of these days I'll take some time to figure out if there's  a "silver bullet", but my guess is the answer is an expertly designed PCB and really expensive low ESR capacitors for power supply decoupling.  By that time a little daughter board with a charge pump looks pretty cheap and easy.