Connecting positive ground to negative ground

[amnesiac]

After hours of searching the internet I know this subject has been utterly beaten to death.  I understand that to power a positive ground pedal and a negative ground pedal together I need isolated power for each.  What I cannot understand is why doesnt the signal cable between the two pedals cause a short?  If on the positive ground pedal the sleeve is positive (9V) whereas on the negative ground the sleeve is negative (0V), won't this present a problem?   Specifically I am wanting to connect a PNP fuzzrite to any standard negative ground pedal.

[R.G.]

What you describe is why two power supplies are needed. You need two different power supplies, one with the more-positive side connected to ground, and another power supply with the more-negative side connected to ground. For example, for 9V pedals, two 9V supplies connected this way gives a single ground, as they are connected by the shield of the cable as you say, but then one of the power supplies gives a +9V supply for the pedals that use negative-side-ground, and the other power supply gives a -9V supply relative to the connected grounds for the pedals that use a positive-side-ground power supply.

In your case, you can connect the PNP fuzzrite to a negative ground pedal as long as the PNP fuzzrite has its own power supply and the negative ground pedal has its own, different power supply.

[MaxPower]

Keep in mind that you are connecting/coupling an ac (audio) signal from one pedal to the next. So it's not completing a dc circuit. While the grounds are connected, there is no other dc path to complete a circuit between the pedals.

I hope that's right....

[GibsonGM]

Right, Max.   And the ground IS common to both pedals.  By looking at what R.G. said above, we see that the center point between a +9v and -9V supply is that ground.  So you don't have a problem.  It's just in how you look at it!  )
   
Sort of like 2 people running around a baseball diamond, one the normal way and one clockwise...home plate is still the 'reference point' for both.