Two circuits with different polarity in one box

[yeeshkul]

Guys i want to put a Rangemaster and Tube Screamer in one box, together with a tuner and some passive switches.
What is the best solution for feeding those two circuits from one source? I can think of batteries and i can think of a proper two secondary winding power source. Is there something else?

[iainpunk]

I just move over the ground on the fuzz face. I leave everything the same, but what used to be the ground is now the V+ and what used to be V- is now ground. The thing still works the same, sounds the same etc.

Good luck, iain

[EBK]

Charge pump voltage inverter (to give you -9V in addition to your +9V) is another way.

[thermionix]

NPN Rangemaster?

[digi2t]

Charge pump voltage inverter (to give you -9V in addition to your +9V) is another way.

+1

[R.G.]

I just move over the ground on the fuzz face. I leave everything the same, but what used to be the ground is now the V+ and what used to be V- is now ground. The thing still works the same, sounds the same etc.

Well, it works the same and sounds the same - until it doesn't. This works often enough that it keeps being posted as a sure fire fix. It fails often enough that it isn't a sure fire fix.

As Yogi Berra is credited with saying - in theory, theory and practice are the same; in practice, they aren't.

There are some PNP circuits that will make excess noise and/or oscillate if you simply tell it that the supply is now signal ground and the old ground is now an inverted supply. In theory, it should not make any difference. In practice, you usually get away with it, but it is getting away with something, not that it always works.

Using a charge pump to make an inverted power supply for the PNP stuff is a lot more certain.

[yeeshkul]

The charge pump it is then. Cheap, simple, ... thanks guys.

[iainpunk]

I just move over the ground on the fuzz face. I leave everything the same, but what used to be the ground is now the V+ and what used to be V- is now ground. The thing still works the same, sounds the same etc.

Well, it works the same and sounds the same - until it doesn't. This works often enough that it keeps being posted as a sure fire fix. It fails often enough that it isn't a sure fire fix.

As Yogi Berra is credited with saying - in theory, theory and practice are the same; in practice, they aren't.

There are some PNP circuits that will make excess noise and/or oscillate if you simply tell it that the supply is now signal ground and the old ground is now an inverted supply. In theory, it should not make any difference. In practice, you usually get away with it, but it is getting away with something, not that it always works.

Using a charge pump to make an inverted power supply for the PNP stuff is a lot more certain.

I have had this failing on me only once, which was resolved by putting a biggass capacitor over the power supply to shunt every bit of oscillation to ground. But you guys have more experience in pedal building so i won't argue.

[R.G.]

Yep, that sounds right. Simply moving what you call "ground" works so often that people will argue with me about it ever causing a problem. Problems occur so in frequently that some people do it blissfully unaware that it can cause a problem, and even recommend it to their friends.

Of the sometimes it happens, using a BFC on the power will sometimes cure it. Sometimes not. I once had an occurrence of it not working, and spent several days tinkering with it and watching an O'scope while trying every black magic trick I knew to fix it, and it stayed broke.

This is typical of symptoms with multiple contributing causes. Fix one possible cause, and it stays broken until you find the contributing cause that's kicking you over the edge today.

[pinkjimiphoton]

I just move over the ground on the fuzz face. I leave everything the same, but what used to be the ground is now the V+ and what used to be V- is now ground. The thing still works the same, sounds the same etc.

Good luck, iain

it works the same UNTIL ya try to turn your guitar volume all the way off and it becomes a volume-pot-tuned oscillator.


not always, but enough to be ridiculously annoying sometimes.  a huge cap strapped across the power supply can help tho.

[pinkjimiphoton]

a charge pump will work, BUT it can also introduce noise and a high pitched whine that can be really freekin annoying on some circuits. i forget which is which, but on some you can add a cap to get it above auditory range, or short a couple pins together. like everything else, its gonna be a compromise.
me? i'd just make the rangemaster npn. easy breezy.

back to the BFC.... i've gotta agree with RG, i've gone as big as 1000uF and still had oscillation problems in fuzzfaces. to me, if i can't turn my guitar down/off, its a dealbreaker.

i just bought a "fuzzface kit" recently on ebay cuz i was bored, it had everything, and was under 20 bux shipped. all was well til it came time to wire it. as shipped, its a pnp ff wired as suggested.

i used every freekin ge pnp in the house and couldn't get it to NOT oscillate when i turned my guitar down.
finally ended up going hybrid, which i don't like to do.