Question about negative ground for fuzz

[add4]

Hey folks,

I'm thinking of building my first fuzz on turret board, i have everything ready, but i still have one question :
I hate batteries, they're not ecological, you have to open the boxes, it's heavy, and expensive.
I would like to use a power supply for this fuzz, but i don't get why i need to road rage to power this with positive ground. Can't i just use my regular power supply and solder the positive wire of the circuit to the ground of the DC jack and the ground of the circuit to the +9v lug of the DC jack?

From what i gathered it can't be so simple.. but why?

[alanp]

The problem arises when you need to connect negative ground (or +9V circuits) to the same power supply as your positive ground (or -9V) circuit.

[add4]

Ok.
that's something i can understand even if i don't see why it would be a problem like that .. but i can accept theres something i don't know that would be a problem :p

[crash]

You do not need -9Vdc for PNP type fuzz pedals.  All you need to do is build the pedal "upside down".  Connect the +9Vdc to where "ground" would normally be and connect the 0Vdc to where the +9Vdc would normally be.  Flip the polar caps around.  That's it. 

The circuit does not care if you have +9Vdc or -9Vdc.  All that matters is that there is a -9Vdc difference between "ground" and "power".  See the schematic below.  Same technique works for fuzz faces, tonebenders, etc.

These pedals work fine with any other +9Vdc pedal.  The "tip" is still the guitar signal and the "sleeve" is still 0Vdc.

[JakeFuzz]

A PNP fuzz circuit wants to see a negative voltage potential as opposed to the NPN fuzz which operates under a positive potential. This just means that instead of going from +9 to 0 volts like we usually see, PNP goes the other direction from -9 to 0 volts. This would all be fine if we were able to easily make a -9V potential (charge pump) and reference the grounds from the same point (0V).

The easiest way to operate the PNP fuzz is to now make 0V where the positive supply normally is and the +9 volts where the ground was. This gives us (0V - (+9V)) = -9V  which is what our circuit wants to see.

The problem with this is if you remember our jacks and patch cables connect all of our pedals together at one common ground. Now if we use a common supply between all of our pedals (one spot), in one of our normal pedals we have our standard ground at 0V but in our PNP fuzz we have our ground at +9V. You see we have essentially shorted the power supply causing (theoretically) infinite current to run through it and now our one spot hates us. This is why you see people converting to -9V using a charge pump so we can all reference from the same ground as most other pedals.  

[TNblueshawk]

A PNP fuzz circuit wants to see a negative voltage potential as opposed to the NPN fuzz which operates under a positive potential. This just means that instead of going from +9 to 0 volts like we usually see, PNP goes the other direction from -9 to 0 volts. This would all be fine if we were able to easily make a -9V potential (charge pump) and reference the grounds from the same point (0V).

The easiest way to operate the PNP fuzz is to now make 0V where the positive supply normally is and the +9 volts where the ground was. This gives us (0V - (+9V)) = -9V  which is what our circuit wants to see.

The problem with this is if you remember our jacks and patch cables connect all of our pedals together at one common ground. Now if we use a common supply between all of our pedals (one spot), in one of our normal pedals we have our standard ground at 0V but in our PNP fuzz we have our ground at +9V. You see we have essentially shorted the power supply causing (theoretically) infinite current to run through it and now our one spot hates us. This is why you see people converting to -9V using a charge pump so we can all reference from the same ground as most other pedals.  

Just have to say I love reading your explanations of things.

[JakeFuzz]

Just have to say I love reading your explanations of things.

Haha, thanks. I've been in too many classes where you get out scratch your head and wonder what the heck just happened for the last two hours. My professors call it job security...