DC Jack

[seekup1982]

I'm making a Minibooster and using a Visual Sound 1Spot to power it.  This is mainly because I could find a place to put my battery in my enclosure.  Anyway, I wired the pin to the ground and the sleeve to the positive (neg pin right?).  When I meter them, I only get a fraction of a mV of potential difference.  When I meter the 1Spot, I get 8.85V.  Am I doing something wrong?  I figure if it were a positive pin, I'd atleast get a negative voltage.  Do I need to insulate it from the enclosure as well?  This is the first pedal I've built from scratch that doesn't just use a battery, so I've never used a DC Jack in any of my own effects before.  I haven't had too much time to debug, but if it was a stupid error, then I figured you guys would catch it right away.  Also, I was looking for an explaination about why a DC jack has three prongs when it only needs two?  Is it some sort of auto-off feature?  Thanks in advance for any advice.

Ben

[u1061810]

Hi,
 Yes, you have to insulate the sleeve if you run the positive to it, otherwise it will short to ground.The reason for the three pins is, one is the ground and the other two either let the current come from the battery, or cut that connection when the plug is put in, and take current fron it instead. Smallbear has DC jacks that have the sleeve insulated.

[u1061810]

Hi,
 Yes, you have to insulate the sleeve if you run the positive to it, otherwise it will short to ground.The reason for the three pins is, one is the ground and the other two either let the current come from the battery, or cut that connection when the plug is put in, and take current from it instead. Smallbear has DC jacks that have the sleeve insulated.