Take a look at this jack here:

http://cgi.ebay.com/ws/eBayISAPI.dl...e=STRK:MEWA:BIN

To my understanding, all 9v type pedals use this type of connector for 9v dc power supplies, with a negative polarity in the center of the plug and positive on the outside. But I noticed there are 3 prongs in the back of the jack, what does is that third prong supposed to be wired to in a normal guitar pedal's circuit? I don't think it's the ground. Btw how can I distinguish between the mystery prong and the positive prong? I can tell which one is the negative as it apparently goes to the center but I can't tell the other 2 apart.

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Just use a multimeter to determine which one is hot. Also I'm not sure if that one with the rivet is used in the circuit, it looks like it may be for mounting to a PCB.

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Even through there are 3 terminals you might find 2 of them shorted. Those are the grounds. One of the grounds are supposed to be wired to the chassis in case of a negitive ground failure and in theory help pervent ground loops.

That or its a stereo audio jack. I've seen them made both ways.

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Oh so I should find which two of the three make contact which each other, those are the grounds? Cool. I already ordered one of those a while ago. I should be getting a 1W DIY amp kit this week in the mail too, it runs on 9v (batteries) so I can use that jack to use it with an AC adapter. Can't wait to get it working. I'll be doing tests with 9v batt though, in case something goes wrong a shock wont be lethal.

I have a 1/4" mono jack laying around and there are 3 prongs. There is a tab that is in contact with the part that goes to the plug tip receiver(signal), but it seems like if the receiver was designed to bend away from it when a jack is plugged in. The packaging says mono, closed circuit. Do I only need to solder the ground to 1 of the prongs on that one too?

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You shouldn't have to solder the grounds together. How it works is normally terminal 2 is the ground from the power barrel connector and terminal 3 is wired to the chassis. Ideally both are at the same reference but just in case when the power barrel is removed terminal 3 springs in to contact terminal 2 to act like a voltage bleeder so that ground reference is maintained in both the circuit and chassis. Its a safety measurement in most designs to have this done at several points so that no residual voltage is left standing next time you plug in. The power entry point being one of them.

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Thanks for that. Could you point out which are 2 and 3? And what if I have no chassis and I'm just testing this amp on a piece of cardboard, does terminal 3 need to go somewhere? I might make an enclosure for the circuit out of wood so I won't need to ground anything outside of the circuit I figure?

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I'm guessing that the outside terminal is 3, but as long as you attach it to some other grounded spot in the amp circuit you should be fine. Basically you will have 2 grounds and one hot.

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