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Help with wiring of piezo bridge - battery draining

Discussion in 'Pickups & Electronics [BG]' started by loSbabbaro, Nov 11, 2018.

  1. loSbabbaro


    Nov 11, 2018
    IMG_0309. IMG_0311. IMG_0310. Hi all,

    this is my first post in the community, I hope someone has the expertise to help. Thanks in advance to anyone who takes the time.

    My bass has two passive single coils, a Bartolini preamp (balance, volume with active p/p, bass/high stacked) + a piezo bridge and I have two issues:
    - when there is no battery or a dead battery I cannot play the bass even in passive mode
    - the bass eats batteries even when unplugged

    I suspect it is due to the incorrect wiring and I am attaching picture of the current setting
    I also found this post with a cool schematic but I cannot interpret it lol Battery draining in active bass

    Anyone knows how to rewire to play without battery (not the piezo of course) and to avoid killing batteries in 2-3 days even unplugged?
    A big thank you for the help!

    IMG_0309. IMG_0311. IMG_0309.
  2. bholder

    bholder Affable Sociopath Supporting Member

    Sep 2, 2001
    central NY state
    Received a gift from Sire* (see sig)
    I haven't tried to follow the wiring yet, but the usual trick is to isolate the ground from the piezo and run it through the ring of a TRS jack - that way, the battery is only on when the bass is plugged in. I'll see if I can find a schematic, but there are better experts on here than me that should chime in when they wake up. :)
  3. loSbabbaro


    Nov 11, 2018
    thank you, it may be a stupid question but you mean the ground from the saddles, from the piezo pot or from the piezo mixer?
    I don't even know if my neutrik is a TRS jack lol
  4. loSbabbaro


    Nov 11, 2018
    I did some further research and the connections are as follows:

    - Ground from battery: ring
    - Red from piezo mixer: tip (red from battery and red from preamp connect to the piezo mixer)
    - White from piezo (I assume it is the hot): ring
    - Ground of the cable from the piezo: Sleeve (GR), this is the 'external layer' of the cable coming from the piezo buffer wrapping the white and the red cables from the piezo buffer

    is there anything that should be wired differently? any of the 4 cables going to the wrong one?
    I assume now it is the ground from the battery that should go to sleeve? is that correct?
  5. lz4005


    Oct 22, 2013
    Even if everything is wired correctly, a defective jack can result in the same short term battery drain. Once you verify the wiring vs a schematic, consider replacing the output jack.

    To address your other question: You can't without making big changes.

    If you want the piezo and mag signals to come out of the same jack they need an active buffer circuit to mix them and match impedence. That circuit will not work without a battery.

    You could, in theory, add a second output directly from the magnetic pickups, but that would require drilling holes and possibly adding more controls.
  6. loSbabbaro


    Nov 11, 2018
    thanks @Iz4005, I understand than then the bass will not play in passive mode without a battery
    I am also quite sure the jack is not defective and I think the ground is just wired to the wrong part of the jack
    I think I am going to do some tests over the week-end but if someone with experience can help that could potentially prevent some mistakes :)
  7. byacey


    May 16, 2008
    Alberta, Canada
    For the jack to properly switch the battery, nothing except the negative wire from the battery should be connected to the ring terminal. All other grounds should be connected to the sleeve terminal. Only the signal output wire(s) should be connected to the tip.

    If the jack isn't connected this way, chances are you have other problems too, as whoever wired it didn't know what they were doing.
  8. loSbabbaro


    Nov 11, 2018
    perfect, that sounds like I need to re-do the soldering of the signal from the piezo
    thank you all and I will update the post with the outcome
  9. loSbabbaro


    Nov 11, 2018
    I tried to wire the signal from the piezo to the tip and no sounds come out from the piezo if I do it, that is really weird as the magnetic seems to be wired there and no problem

    I also tried my luck wiring the piezo wire to the sleeve but nothing happens

    the only way to have sound from the piezo is to wire it to the ring, where the black wire from the battery is, but that closes the circuit and kills the batteries

    I am really hopeless with this thing, that close to gut everything out but I really like having the piezo sound...
    Attached the schematic from Neutrik, but I think I have understood it

    Anyone has any idea?

    Attached Files:

  10. byacey


    May 16, 2008
    Alberta, Canada
    I'm not sure how you could possibly get any piezo signal wired the way it is. The ground / shield of the piezo should be connected to ground (sleeve of the 1/4" connector) and the hot would have to go to the signal input of your onboard preamp.
  11. I think there might be a separate switch in that jack for the battery. I have a Fishman powerbridge and a different pezio system in another guitar that can send the signals to the tip and ring terminals of a stereo cord and also switch the battery on and off. One of them is apart. I'll look at it when I get home.
  12. loSbabbaro


    Nov 11, 2018
    thanks guys, it so difficult to find someone around here to fix this kind of stuff
  13. 765F801E-C2F6-4397-A887-DEA7CAB26D94.

    Sorry it took so long to get back. I had some time to work on things yesterday and I did that instead.

    GraphTec uses the open frame jack above with an extra normally closed switch that turns on the battery when it opens. Not sure on the exact function on that. As you can see, it plugs into their board. Here’s some more info: http://www.graphtech.com/docs/default-document-library/ghost-installation-manual.pdf?sfvrsn=4

    Fishman uses a 9 pin jack on the Powerchip. That has an extra switch in it also but, again, not sure on the exact function of the switch and I can’t find the one I had. I forgot, that the last time I put that Powerbridge on a guitar I wired it up as passive, no battery. Again, more info: https://www.fishman.com/wp-content/uploads/2018/07/009-074-001_r1-User-Guide-Powerchip.pdf

    Don’t know if any of that helps but it does show you can have signal at the tip and ring terminals and still turn a battery off and on. Seems like it just requires some additional electronics which you may or may not have.
    loSbabbaro likes this.
  14. loSbabbaro


    Nov 11, 2018
    thanks Matt, that is really helpful!
    I think my piezo is a fishman, I will look at the schematics and maybe I will buy the extra bit if needed then
  15. You can look around some more on Fishman's website. The Powerchip should be able to be used with any piezo and magnetic setup.
  16. byacey


    May 16, 2008
    Alberta, Canada
    Switchcraft does make jacks that have some different variations of switching contacts, some isolated, some not.
    However, if signal is meant to be sent out on the ring terminal, this requires a TRS 1/4" plug, and some unique device specific to this instrument to recover the piezo signal at the other end of the cable for amplification and mixing. A standard 1/4" tip sleeve connector isn't going to do it.
  17. Yes. The picture is a TRS jack with a switch but it needs the GraphTec electronics to work properly. I thought the Fishman jack might help the OP but I can't find mine to test what the switch does and I suspect it needs the Powerchip to work properly.
  18. Bartpop


    Mar 5, 2019
    Fishman makes an Endpin jack called a Switchjack that has 4 lugs, compared to the 3 lugs of a standard stereo jack. Wiring the battery negative to the 4th lug (Switch lug) will prevent the battery from draining when you're not plugged in, and you'll still be able to split the mag/piezo signal when needed. That's the way I wired my banjo, using a Powerchip mixer to combine the output of a P-90 Stack pickup with a couple of piezo transducers. I've been using the same battery for over a year.
    Last edited: Mar 5, 2019

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