bipolar / non-bipolar power supplies

[Ashurbanipal]

Elementary question here, but I can't seem to find an answer so far anywhere.

What's the difference between a bipolar power supply and the other kind, and why aren't they interchangeable? And how can you tell which kind a 9/12v adapter is?

The specific problem I'm having is that I have built a project that requires the non-bipolar and one that requires bipolar. If I run either box separately from an adapter I have, they both work. If I run them together and chain the audio in series, they both die. If I run the non-bipolar one on a battery, and the other on the adapter, and chain the audio in series,  they both work great. I don't want to use batteries, and I don't really want to build a power supply since they're so cheap, but I can't seem to determine if the ones at radio shack are one kind or the other.

[NoFi]

Maybe one of your projects is "positive ground" (old fuzz circuit ?), and the other one is the standard negative ground so if you power those two projects from the same power supply you are shorting things out. I have an old positive ground big muff from 76 and that's what happens.
If that's your problem, what you could do is power the positive ground pedal through a -9V charge pump. That's what i'm going to do mith my big muff. And then all my pedals will *normally* work from a single power supply.

http://www.geofex.com/circuits/+9_to_-9.htm

[no one ever]

bipolar power? never heard of it...

[Ashurbanipal]

That's not it NoFi, but thanks. One is negative ground with two connections + and ground, and the other is bipolar with three separate connections +, -, and ground.

no one ever, you're not alone. Neither has radio shack or the guy at the guitar amp place in town that doesn't suck. Here's a project page for one: http://www.generalguitargadgets.com/index.php?option=content&task=view&id=191&Itemid=216.

[R.G.]

"Bipolar" means literally "two polarities", and in reference to power supplies, it means that there is one ground reference point and two (usually equal) power supply voltages on each side of the ground reference.

For instance, a 9V battery is a uni-polar ("one polarity") power supply. You can connect either the + or the - side to ground. If you connect the - side to ground, you have the standard negative-ground power that most effects use. If you connect the + terminal to your circuit ground, you form a positive ground power supply like the Fuzz Face and some other germanium transistor effects need.

If you connect the + side of a battery and the - side of another 9v battery together, then the three terminals form a bi polar power supply. The two common terminals is the ground terminal, and then the free + terminal is the + side and the free - terminal is the - side.

You can also make a bipolar power supply from an AC power source by rectifying and filtering appropriately. The article at GEO on Power Supply Basics explains a lot of the, but most people can't be troubled to read the info there.

Sticking "bipolar power supply" into google turns up web pages pretty quickly that tell about +/- voltages.

[NoFi]

Bipolar power supply, i see. I was thinking of reverse polarity. 

But i dont see why Ashurbanipal has problems when he connects his bipolar power supply to his unipolar pedals. Should it not work as long as he just brings the +9V and ground to the non-bipolar pedals ?
Interesting matter anyway. 

[R.G.]

But i dont see why Ashurbanipal has problems when he connects his bipolar power supply to his unipolar pedals. Should it not work as long as he just brings the +9V and ground to the non-bipolar pedals ?

It should work, and it would if (a) the bipolar power supply is running correctly and (b) he does not short the power supply out by the way he connects the unipolar pedal to the bipolar supply. It's easy to connect signal ground to the wrong place, shorting one side of the bipolar.

[Ashurbanipal]

The unipolar effect works with the adapter by itself. The bipolar effect works with the adapter by itself. It's when both are powered up by the adapter and audio chained in series that they die, and not suddenly like something's shorted to ground. I don't even know if this adapter is bipolar or unipolar since it doesn't say. When I power the unipolar by battery, and the bipolar by adapter, they work with audio in series. Maybe it's bot a unipolar/bipolar problem.

[bioroids]

I never seen a bipolar adapter.
How many output leads does it have, and what kind of plug?

Miguel

[jrem]

maybe the original poster meant "regulated" vs "unregulated"?

[R.G.]

Ashur - do you mean "AC adapter" where you're saying "bipolar adapter"?

Unipolar adapters have two wires, one positive and one negative. Bipolar DC adapters must have three wires; one ground, one + and one -.

[bioroids]

How do you conect both pedals to the same adapter?