DC Brick - Making a custom cable?

Discussion in 'Effects, Pedals, Strings & Things' started by highfive!, Oct 6, 2008.

  1. highfive!

    highfive! Member

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    I have a pedal (Janglebox) that runs off a 9v center pin positive adaptor. Can I take one of the standard cables from my DC Brick, chop it up and reverse the ring and tip wires so that I can use the Brick to power this thing?
     
    Last edited: Oct 7, 2008
  2. cvansickle

    cvansickle Supporting Member

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    It only works if the power outputs on the power supply are completely isolated from each other, like on a Voodoo Lab Pedal Power. I believe the DC Brick is a daisy chain supply. It requires that all your pedals have the same polarity.
     
  3. highfive!

    highfive! Member

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    Yes, the DC Brick is a daisy chain supply. And the supplied cables are center tip positive.

    Hmm. I read this on a review somewhere:

    "I made a battery eliminator cable for this pedal by cutting and reversing a DCBrick cable... I think they should supply a DC cable if they are going to offer such an odd hookup configuration."
     
    Last edited: Oct 7, 2008
  4. highfive!

    highfive! Member

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    I don't know much about electricity, but common sense tells me that in this case it doesn't matter where the current is coming from (be it isolated or daisy chain), it just matters where it ends up. In other words, if I reverse the wires, the same current is flowing, but what once went to the tip, is now flowing to the ring, and vice versa. This would make the cable tip positive, and I could now use the Brick with this "new" cable to power my pedal, no?

    Edit: In fact, I've been running a Demeter Compulator, which uses a tip positive mini-plug, in a daisy chain with other tip negative pedals without any problems. In this case I took a 1-Spot 5 plug daisy chain cable, ran 1 plug from the extra DC output of my Pitchblack, hooked up 3 other center neg pedals, taped up the remaining plug on the daisy chain, and used the "power input" plug on the 1-Spot daisy chain to power the Compulator by flipping around a standard DC Brick cable (so that the male mini-plug end - which would be tip positive, right? - goes into the pedal, and the tip negative end is connected to the power).

    Damn, this sounds more complicated than it should.
     
    Last edited: Oct 7, 2008
  5. zachary vex

    zachary vex Member

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    Daisy-chain negative-ground power supplies cannot provide positive ground under any circumstances.

    Picture it this way. Your whole pedal chain has negative ground flowing through the cable plug casings and shields. You flip one power supply connector and now the ground on that pedal is positive... but when you connect the power, the positive from the supply shorts directly to every other pedal's negative ground through the modified connector and because your whole power supply is dead-shorted to ground, it either starts on fire, stops working, or it blows the internal fuse. If there is one.

    Isolated output power supplies have independent grounds on every output. They float free, independent of each other, so they can be inverted without conflict.

    Daisy-chain power supplies have common grounds because all of the outputs are wired in parallel. Their negative sides are all chained at the ankle. They don't float, and they can't be ground-inverted because they're tied at the ankle. But they're cheap, and they work as long as there's no positive-ground devices needing power in the chain.
     
  6. highfive!

    highfive! Member

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    Thanks Zack, that makes sense. But then why is the "edited" part of my last post working for me, and not starting any fires?!

    And why does Godlyke state this for their "Power-All" - "Includes Cable-5 daisy chain connector and assorted jumper cables to power phone plug, reverse polarity, battery-only, and Line 6 units." http://www.stompin-ground.com/products/sgpowerall.htm

    So confused.:messedup
     
  7. highfive!

    highfive! Member

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  8. highfive!

    highfive! Member

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    Anybody make sense of this?
     
  9. cvansickle

    cvansickle Supporting Member

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    The 1-Spot "Converter" is really just an "adapter." It lets you put a center positive pedal on the 1-Spot so that the polarity is correct for the power supply and pedal. However, you still cannot put a positive center pedal on the same 1-Spot chain (it is still a daisy chain) with all your other negative center pedals.
     
  10. highfive!

    highfive! Member

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    Ok then why does this diagram show otherwise? The black cable is center negative, and the red and green are reverse polarity...

    [​IMG]
     
  11. cvansickle

    cvansickle Supporting Member

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    Yes, their advertising would have you believe this is possible. They are lying. Believe me, I own a 1-Spot, the adapter, and three different center positive pedals. It doesn't work.
     
  12. highfive!

    highfive! Member

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    Well, I talked to Steve at Janglebox, and he actually sells the 1-Spot adaptor cable with a poisitve tip exactly for the reason I'm posting. He's telling me that there's no problem running both polarities off a daisy chain power supply. :dunno

    But anyway... if I go ahead and give it a go, rewiring my own cable to reverse the polarity, will I run the risk of frying anything, whether it works or not?

    Thanks for the help.
     
  13. bh.

    bh. Member

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    This is weird and I've always been confused too... Because I've been able to power +tip pedals (dod envelope filter/ehx big muff) alongside -tip pedals (most pedals) using the godlyke/1spot adapter cables. I've done this using a dc brick and a 1spot with no problems at all. I hope someone could explain too. Thanks!
     
  14. jnepo1

    jnepo1 Silver Supporting Member

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    Godlyke does offer the reverse polarity adapter and states you can run the different polarities thru their PSU. However, the point people are trying to make is, if you do mix the polarities in your PSU, you are risking a higher probability of have noise issues. That's why I prefer to have a PSU w/ isolated outs.
     

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