"Negative Ground" newbie question

[moritz]

Hi all,
I am about to embark upon my first stompbox project, a Ge Fuzz Face clone, and have a somewhat "newbish" question regarding making a PNP circuit with negative ground...

From what I have read, having a negative ground allows me to use the same power source as many of my other common pedals. I'm assuming (and I may well be completely off the ball here) this means that at the power (9V) input jack, the center pin will be negative, and the outside sleve part positive (like on boss pedals). However, when I look at the various PCB layout pictures that I have found, it appears that the positive ground version of the same circuit also has this negative center pin/positive sleve configuration at the power input jack.

Could someone please clear me up on this? Why does a negative ground allow me to use a common power supply with my other pedals as opposed to a positive ground circuit? Any help on this would be greatly appreciated. Many thanks!

[Transmogrifox]

The wire that connects ground is interconnected through all of your pedals via the sleeve of the jack.  If you connect the positive terminal of the same power supply to ground in one pedal, yet have the negative terminal connected to ground in another terminal, you have a short through your common ground and will likely burn up your power supply or something unfavorable dealing with heat, smoke and fire...or maybe just blow the breaker on the protected power supplies.  

It doesn't matter how the power comes in on the jack (whether negative middle, positive outside or vice versa)--it matters where you connect those into the circuit inside the box.

Does that help at all?

[Sic]

With negative ground, the center pin is positive, and the outside part is negative.

Personally i like messing with stuff that has a negative ground, just for the same reason you mentioned it,  you can use alot of regular 9v wall warts.

[Sic]

see how the + is in the middle

and the - is around the outside (sleeve)

[moritz]

The wire that connects ground is interconnected through all of your pedals via the sleeve of the jack.  If you connect the positive terminal of the same power supply to ground in one pedal, yet have the negative terminal connected to ground in another terminal, you have a short through your common ground and will likely burn up your power supply or something unfavorable dealing with heat, smoke and fire...or maybe just blow the breaker on the protected power supplies.  

It doesn't matter how the power comes in on the jack (whether negative middle, positive outside or vice versa)--it matters where you connect those into the circuit inside the box.

Does that help at all?

Ok, thanks very much, that makes a lot of sense now. However, it does lead me to one further question... Does this cause a problem if I connect a chain of negative ground effects which all use a common wall wart, to a positive ground effect which is running on a battery. Wouldn't this cause a problem in that the negative terminal of the wall wart would come in contact with the positive termanal of the battery?

Again, thanks heaps for the help.