Adding a voltage bias to + ground?

[jallenfuzz]

I was interested in adding a voltage bias for a Tone-bender and the pedal is wired positive ground, there are two wires that go to ground on the circuit board. One is from the battery's negative terminal and the other is from the negative terminal on the DC jack.  The rest is the positive ground. I am not sure as to whether to put the bias pot on the negative or positive? Any help?

[aron]

If it were positive ground as you say, the + terminal would be connected to ground.

[PRR]

> pedal is wired positive ground
> go to ground ...from the battery's negative terminal
> other is from the negative terminal on the DC jack. 
> The rest is the positive ground.

Sure sounds Negative ground to me?

Or just not wired the way you think it is?

[jallenfuzz]

I think I'm misunderstood, the pedal is wired positive ground.  I have put a voltage bias on a typical negative ground pedal.  Which is a potentiometer that regulates the incoming voltage to the circuit. Some call it a voltage sag.  I was wondering how I would implement that on a pedal that uses a positive ground.

[anchovie]

That's not voltage bias - if you've got a pot wired as a variable resistor to reduce the supply voltage then that's a Starve control. So for a positive-ground pedal, you want that between the negative supply voltage (i.e. not ground) and the point where that voltage supplies the circuit.

[pinkjimiphoton]

put the pot between negative power supply and negative on the board. same as you would for a positive starve control.

you can kinda call it a bias, but bias generally affects each semi separately... this would starve the whole pedal... which definitely will change the bias, but not the bias point.

[jallenfuzz]

Thanks guys, that's what I was thinking... I just wanted an opinion before I tried it..

[jallenfuzz]

Hey thanks again guys, it's working good.  It has a different flavor than the same pedal built with a typical negative ground, it's interesting, I have to play it some more.