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reverse polarity(positive ground instead of the usual negative ground)?

Discussion in 'Effects, Pedals, Strings & Things' started by Melodic Dreamer, Nov 28, 2005.

  1. Melodic Dreamer

    Melodic Dreamer Member

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    Okay, I emailed MJM about ordering info and asked them a question about their power supply. Here is what he wrote back.


    Okay, please forgive my stupidity, but what exactly would I need to buy then? :confused:
     
  2. StompBoxBlues

    StompBoxBlues Member

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    I'm with you....this person is not writing precisely or clearly enough to be sure of what he is saying. You should write back and ask for a simpler explanation.

    Ask for specifics, it is no help at all to tell you you need "a special cable attachment" without telling precisely what the attachment does, how it is wired.

    I don't know if the main question is on the "roctavio" or the "octave pedal like a Tychobrae"...in what context was he responding, what question from you?

    In general, mixed with common sense (I think) I'm getting the following:

    You MUST NOT use one of those daisy chains, because the center pin is negative on those, so you would be hooking up a negative directly to a positive voltage.

    When he talks about a regular power supply, I am pretty sure you need a special cable even then if he expects positive on the center pin....this is the WHOLE crux of the situation, you need to know for sure if this is what he is saying, his pedal expects postive voltage on the center pin?

    When he talks about isolated outputs, he means like the Big John, or Brick, that have audio plugs on the supply, with like 7 outputs, and each is it's own, and the cables that come with these switch negative from the audio connector (what's it called...RNC?) OUTSIDE, to the negative barrel style middle pin that goes into the pedal. The reason they have it crossing like that is, it would be dangerous if the outside RNC connectors were positive, if a paper clip got between them it would short...so they have negative outside, but still, the main thing is they convert in the cable so it becomes negative center pin where it counts...on the way into the pedal. (hope I'M not being confusing now..main point is) so I think he just means, if you have a multi-output power supply, you have to have a special cable that keeps it center pin positive, and ALWAYS USE ONLY that one cable for that one effect. Which is basically, fraught with peril, that one night you are setting up and accidentally plug the wrong one in.

    If I were you I would aski him to clarify, and if I have it right, I would absolutely buy a seperate power supply for use ONLY with that pedal.

    I don't know what that also is going to do with ground loop problems. To be honest, I wouldn't buy a pedal that decided it was smart to go against the industry standard....it doesn't inspire a lot of confidence in the maker.
     
  3. Jim Collins

    Jim Collins Member

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    Voodoo Labs Pedal Power does have isolated outputs. This means the Pedal Power can be used to power both types of pedals -- negative ground and positive ground -- at the same time. You will need to construct your own positive ground cable, though. This is very simple to do. All you have to do is take one of the power cables that comes with the Pedal Power, cut it in half, and reconnect, but in reverse. This new cable, then, can only be used with the positive ground pedal. (Voodoo will sell you a positive ground cable, but it is cheaper and quicker to do it yourself.)

    I've done this with a Pedal Power, and it works as advertised. There are more than a few pedals out there that are positive ground. Some manufacturers, such as Fulltone, make both kinds. In the case of the Fulltone pedals, they are being faithful to the original pedals upon which the circuits are based.
     
  4. Melodic Dreamer

    Melodic Dreamer Member

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    Thanx guys for the help, and trying to explain this to me. I'll admit, I'm not the most mechanicle minded person. It's hard for me to understand why someone would build something out of the norm. I know you guys mentioned the pedal power two, but I don't even have that.

    In the beginning I was trying to decide between the MJM and the Addrock. I think I might buy the Addrock just so I won't have to deal with this. I was really wanting the MJM from the clips I heard.
     
  5. Melodic Dreamer

    Melodic Dreamer Member

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    Wow, I think the Addrock is the same way.

    Okay, so if I buy either I have to use a certain power supply, right? Will a normal boss adaptor work, if not direct me to an adaptor on-line to buy. Yes... I'm the gearpages retard:dude


    lol forgive me guys.. I just play!:D
     
  6. Moe45673

    Moe45673 Member

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  7. theelectic

    theelectic Guest

    That's what it amounts to. It's not clear because you don't understand the concept of grounds. You can use it with any adapter, but the adapter cannot be daisy chained to anything else. One BOSS PSA type to power the pedal, no daisy chains, nothing. If you're one of those who use a Powerall/Onespot/etc. and a daisy chain to power all their pedals, you'll have to use a completely separate adapter just for your positive ground effects.

    That IS the industry standard for positive ground effects. Again, most pedals have a NEGATIVE ground. The black wire of the battery goes to ground, and the red wire goes to power your effect. Some effects have POSITIVE ground, whre the red wire goes to ground, and the black wire powers your effect.

    Imagine if you're using a BOSS PSA adapter with a 5 spot daisy chain. If all five of those pedals are negative ground, then all the daisy chain is doing is splitting the adapter output to each of the five pedals. Think of the single BOSS PSA adapter as one giant 9V battery, and all 5 effects are being run off that single 9V battery (each output is not isolated). Say you remove one effect and replace it with a positive ground effect - well now, what you've done is the RED wire (positive) goes to ground (through the positive ground effect), and the BLACK wire (negative) also goes to ground (through the four other negative ground effects) which means you've created a short, and therefore no power for your pedals!!!

    An adapter like the Voodoo Lab Pedal Power series is like having eight (or more) individual, separate 9V batteries on each output. In other words, each output is it's own "battery", and each "battery" does not affect/interact with any other battery. So if you're using this type of power supply, you can go ahead and plug any type of effect into any of the outputs, and as long as you don't split off the output, you'll be fine.

    Bottom line, the maker said to use a BOSS PSA, use a BOSS PSA *just for that effect*. Don't hook any other effects to that one power supply.
     
  8. StompBoxBlues

    StompBoxBlues Member

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  9. nlopez

    nlopez Silver Supporting Member Supporting Member

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    OK guys. Answer me this:

    I have a Signal Flex power supply . They are not isolated outputs like the Pedal Power, but it's like the Brick. It has 5 outputs. All of my pedal are negative ground and utilize 4 of the outputs and some are daisy chained. I have one postive grounded Voodoo Labs Micro Vibe and had a cable re-wired as was mentioned to use with this pedal on the fifth output of the Signal Flex. Is this OK?
    Granted, I have been using this pedal board as is for about 9 years
    Thanks
    Nick
     
  10. Melodic Dreamer

    Melodic Dreamer Member

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    Thanx for the great insite guys, i'm trying to soak it all up.. In a way I think I kinda got it now. :)
     
  11. Matt Gordon

    Matt Gordon Senior Member

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    The DC Brick is just a daisy-chain to the power supply, so just using a reverse cable wouldn't work. You need an individual power supply AND the reverse cable, or just the reverse cable and the Voodoo Labs ISO supply, whats it called, PS2?? Yes, yes!!?
     
  12. theelectic

    theelectic Guest

    Correct. Even if you swap the cable's terminals around, it doesn't do anything to the actual effect it's powering. If the effect is positive ground, no matter what it's going to be grounding the positive (red wire). If the other effects need that red wire for power, you just shorted that power to ground, and nothing will work.
     
  13. nlopez

    nlopez Silver Supporting Member Supporting Member

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    "Correct. Even if you swap the cable's terminals around, it doesn't do anything to the actual effect it's powering. If the effect is positive ground, no matter what it's going to be grounding the positive (red wire). If the other effects need that red wire for power, you just shorted that power to ground, and nothing will work."

    Matt and theelectric,

    I believe what you both are saying. It makes sense and I am not arguing the contrary. What is confusing it that I have been doing this for years and I cannot understand why.
    There has to be some missing factor in the equation, 1)the Signal -flex IS actually isolated. (I don't think so) or 2)the Micro vibe is standard, (but the cable has been reversed)

    I did bring this up with to a guy at Voodoo Labs years ago and the person I spoke said with the reversed cable it could be done.
    But from everything I read indicates what you both are saying. I don't know?

    :(


    Thanks,
    Nick
     
  14. theelectic

    theelectic Guest

    I'm 99.999% sure that the Micro Vibe is a normal negative ground effect. AFAIK the only odd ball in the VL lineup is the Proctavia. And the Micro Vibe uses the industry standard center negative, same with the Signal Flex, which for the price I presume is not isolated. Strange. Maybe the special cable you got isn't so special? If you have a multimeter handy, check for continuity between the outside ring of each end. If they're connected, then the cable isn't switching anything.
     
  15. nlopez

    nlopez Silver Supporting Member Supporting Member

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    That has to be the case. It uses the little dunlop input and not the Boss type. Maybe that is what has happened. Thanks for the advice.

    Melodic, sorry for hijacking your thread
    Nick
     
  16. WahmBoomAh

    WahmBoomAh World Crass Guitarist Silver Supporting Member

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    ok experts ....what about this one . I just bought a janglebox from matt off tgp and he says it's got the tip backwards polarity wise too ...it's still in the mail ..BUT to those who are familiar with the janglebox ....will I have any problem with the ADL juicebox (ver 2) there are iso inputs but it would have to share power blocks with someone else on the board ....THANKS
     
  17. Melodic Dreamer

    Melodic Dreamer Member

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    No problem, I'm just glad that there is someone else who needed help. lol I honestly felt stupid asking this question. In a way I kinda figured everyone would end up being like, You don't know this!?! lol
     
  18. dyer_maker

    dyer_maker Member

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    Can't mix and match polarities on a single ISO output. Have to separate them. You will have problems, a short and none of the pedals connected to the output will work. Although the PP2 has less mA per output it is nice to have 8 isolated outputs if you have negative and positive polarity effects. I have a Juicebox as well and have moved away from positive ground effects, only have a McFuzz now.
     
  19. theelectic

    theelectic Guest

    Let's make a differentiation here: the TIP of the PLUG can be center negative or center positive. Doesn't really matter if that's what the effect is designed for. However that's completely different from the effect having a negative ground or positive ground. If you look at any other adapter that uses a barrel type connector (from a keyboard, recording box, whatever) chances are it's center POSITIVE. The BOSS standard (which is the standard of almost all FX) are center NEGATIVE. Don't ask me why this is the case, it just is :)

    Now if the Janglebox uses a center POSITIVE plug, it's backwards from most of the other pedal FX on the market, however I'm again 99.999% sure it's a negative GROUND effect (every Dynacomp derivative is), so you should be fine as long as you mix it with other negative ground FX, and observe proper polarity (of the PLUG) when plugging power into the Janglebox.
     
  20. TBone

    TBone Member

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    If you haven't already done so, dedicate one of the smaller iso channels on your JuiceBox for the backwards polarity pedal. Then you still have the larger iso's for the bulk of your rig with tip (-).

    The ADL JuiceBox was designed with exactly this in mind. The idea that not every pedal has to be isolated but some do. That's why there is substancially larger capacity per iso channel than something like the PP2. There are 5 iso's but in most cases, you could run a lot of pedals on iso 1 or 2 with up to 500mA per channel available (more pedals than the 4 output jacks on each iso by adding the "Y" cables / splitters) This also allows for the more frequently occuring pedals that require more than 100 or even 200mA to power.

    Pedalgear.net is now produciing the new JuiceBox #003 with a total of 3000mA - more power than ever before but still 5 iso's like the earlier models.

    So a chance here for some valuable opinions - if 5 iso channels isn't enough for most situations, how many do you feel is the right number? At a low 100mA per iso, you could have 30 isolated outputs. But you couldn't power the pedals that need the heaftier supplies.

    TBone
     

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