Ashamedly...I am actually an electronics techincian, but haven't thought enough about this and wondered if someone else know...I ought to know, but am a little unsure. Three scenarios... 1) two battery driven fuzz pedals, one with PNP (and positive ground to pedal), the other NPN (with negative ground on the pedal)...the two pedals make contact...what, if anything happens? 2) One battery driven positive ground, one powered (from "the brick" or another power supply) negative ground pedal make contact...what happens? 3) Both running from ONE DC power supply, with one negative (normal) ground pedal, and the other adjusted cable for it being positive ground..the pedals make contact...what happens? I mean, voltage is the electrical potential between any two points. It is relative (usually ground, but also relative to other points)...but if you place two 1.5 batteries with positive going to negative on the next you make a larger voltage (3 volts), if you place them positive to positive and negative to negative, they sum to 0 volts...(but lotsa current and probably nasty things)... But I have not thought enough about pedals, their chassis grounds and relative to the signal that passes through them. So, can any knowledgeble person clarify for me a little of this...especially if they can damage the pedals if they end up touching each other?