Silly question I never understood from reading articles about positive ground pedals

[GrooveChampion]

How come positive ground pedals(Germaniums usually) can work on a regular 9V battery?

[nostradoomus]

I would imagine its because with a battery you can wire the polarity however you want but with a power supply its always center negative.

[GrooveChampion]

Thats what doesnt make sense to me, wiring a power supply the other way around simply doesnt work.

[scimitar]

It's because a power supply is grounded via the mains, as is your amp, and the negative of the power supply is (normally) connected to the mains ground, therefore the negative has to be the ground. With a battery, neither positive or negative is connected to ground so you can connect the positive to ground which effectively makes the negative 9v less than ground i,e -9v.

[GrooveChampion]

Thank you kindly sir.

[induction]

scimitar wrote

It's because a power supply is grounded via the mains, as is your amp, and the negative of the power supply is (normally) connected to the mains ground, therefore the negative has to be the ground. With a battery, neither positive or negative is connected to ground so you can connect the positive to ground which effectively makes the negative 9v less than ground i,e -9v.

Sorry to disagree. Adapter outputs are not grounded. They float just like a battery. There is no DC pathway between the mains and the adapter output except via the amplifier.

GrooveChampion wrote

wiring a power supply the other way around simply doesnt work.

It's not clear to me what you mean. Are you trying to convert an existing positive ground circuit to negative ground by reversing the adapter connections? That won't work. Do you have a negative center pedal and a positive center adapter? Reversing the connections will work.

In general, 'center negative/positive' and 'negative/positive ground' are separate issues, and have to be addressed independently. You can have a negative or positive center on any single-rail pedal, positive ground or negative. You just have to design it appropriately. Negative center is just a convention, it has no impact on the electronic operation of the circuit.

Negative vs. positive ground, on the other hand, is built into the topology of the circuit. If you want to change it, you have to redesign the circuit.

[Gabi Smith]

Hello,

Maybe if you think in term of black and red, it will be easier. Your battery and your power supply have a negative point and a positive one. To know who is who, trust your voltmetre. The negative is the black side and the positive is the red side. In most of the circuits, you will connect the black to the ground. In few circuits (mainly the one that use pnp transistores), the red is connected to the ground. In that case, the electrolytic capacitors have to be turned in concequence.