Positive Ground vs Negative Ground

[Baktown]

I have a friend who wants to use some pedals I built him in his board, but most of his pedals are vintage and are PNP (positive ground).

How in the world can these all work together on the same board?  Use batteries for some ,and wall wart for others?  This has been bothering been since the dawn of time (at least an hour or so).

Rick J

[iaresee]

Use batteries for some ,and wall wart for others?

Just don't share power supplies. Or batteries. Either works.

[R.G.]

We run into this all the time with people using our 1Spot power supply. They get the $20 1Spot and power all their negative ground effects, then ask us about the positive ground ones. We explain about not being able to use both the positive and negative side of any power supply for ground at the same time, then suggest they:
(a) use batteries for the (probably fewer) positive ground power supplies
(b) buy a $200 power box with multiple isolated outputs
or
(c ) buy a second $20 1Spot for just the positive ground pedals

[mth5044]

You built the pedals, can't you mod them to have the opposite ground layout?

[R.G.]

You built the pedals, can't you mod them to have the opposite ground layout?

Not without either (a) changing the polarity of all the semiconductors and other polarized things in them or (b) risking intractable noise and oscillation problems in some - but not all - pedals built with reverse polarity.

[mth5044]

You built the pedals, can't you mod them to have the opposite ground layout?

Not without either (a) changing the polarity of all the semiconductors and other polarized things in them or (b) risking intractable noise and oscillation problems in some - but not all - pedals built with reverse polarity.

I knew it wasn't just a switch of a wire, but sometimes changing out a few componants is easier then getting a whole new power supply 

BUT, from what I understand, godlyke is coming out with a device that lets you daisy chain positive ground pedals with negative. I forget the name though... something about a dog maybe.

[ralley]

How in the world can these all work together on the same board?  Use batteries for some ,and wall wart for others?  This has been bothering been since the dawn of time (at least an hour or so).

You can always build a -9V power supply adaptor using a charge pump (Max1044).  Connect your power supply to the adaptor and the adaptor then feeds 0V and -9V to the positive ground pedals. 

I've got this on my board to feed my Fuzz Face and Rangemaster clones, works well.

Rob.

[R.G.]

I knew it wasn't just a switch of a wire, but sometimes changing out a few componants is easier then getting a whole new power supply 

It depends on your viewpoint, and whether you'd rather use a soldering iron or a guitar pick. 

BUT, from what I understand, godlyke is coming out with a device that lets you daisy chain positive ground pedals with negative. I forget the name though... something about a dog maybe.

About time. I have designed about a half dozen bumps to go on the end of a daisy chain to isolate the voltage. They all suffer from limitations which I think are too severe to make a product from. I even designed a *capacitive* isolator, no magnetics involved. None of them were ready for prime time without going to about the complexity of the whole new power supply. Then there's the price issue again. It's really hard to make for sale any power device costing a whole lot less.

[cpm]

You can always build a -9V power supply adaptor using a charge pump (Max1044).  Connect your power supply to the adaptor and the adaptor then feeds 0V and -9V to the positive ground pedals. 

I've got this on my board to feed my Fuzz Face and Rangemaster clones, works well.

MAX1044 i think it has 10mA max current output, given that, its not a good idea to use as an external source for several pedals, better as an internal power conversion.
For fuzzes wich eats partically no power it may be ok, but its limit may be reached with just some LEDs

[mth5044]

I knew it wasn't just a switch of a wire, but sometimes changing out a few componants is easier then getting a whole new power supply 

It depends on your viewpoint, and whether you'd rather use a soldering iron or a guitar pick. 

People around here play guitar   

BUT, from what I understand, godlyke is coming out with a device that lets you daisy chain positive ground pedals with negative. I forget the name though... something about a dog maybe.

About time. I have designed about a half dozen bumps to go on the end of a daisy chain to isolate the voltage. They all suffer from limitations which I think are too severe to make a product from. I even designed a *capacitive* isolator, no magnetics involved. None of them were ready for prime time without going to about the complexity of the whole new power supply. Then there's the price issue again. It's really hard to make for sale any power device costing a whole lot less.

There you have it, price. I found the Godlyke product I was talking about, the 'Ground Hound'. For people with money and/or limited space, sure it's a good way to do it, but it's more expensive then just buying another powersupply.

http://accessories.musiciansfriend.com/product/Godlyke-GH1-Ground-Hound-Ground-Isolator?sku=580218

They used to have a picture of it.. not sure what happened.

[petemoore]

BUT, from what I understand, godlyke is coming out with a device that lets you daisy chain positive ground pedals with negative.
  I understand how that can't work. When + is connected to -, a direct short in the PS occurs...think...the pos goes to gnd. on the PNP, and the negative goes to ground on an NPN, to my reconing that is 1 directly shorted PS or two separate floating supplies.

[Baktown]

THanks for all the replies.