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WIRING ....HUM WHEN BRIDGE PUP IS CUT

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  • WIRING ....HUM WHEN BRIDGE PUP IS CUT

    Hi wiring Gurus

    Firstly my usual apology for my inability to produce neat diagrams.. These are of course only extracts simplified to basics.

    Over the past 7 years or so I must have used my schematic for series to parallel plus col cut using 2 push pulls (see Fig 1) around 8 or 9 times without any issues or problems.

    I and several others prefer this wiring to the usual more straightforward option of coil cutting when the bridge pup is in series mode as we consider it gives better options. The option of having parallel wiring for the bridge is beneficial if it is over wound like a JB for clean playing.

    Sadly on my most recent project using this wiring I seem to be getting hum when the bridge pup is cut to the slug coil.I suspect this may be due to some kind of antenna effect as in the diagram the coil cut leaves the bridge screw coil hanging while still connected to the hot.

    This issue will hopefully be removed by adding a jumper wire (see Fig 2) which will connect the hanging wire to the hot side when coil cut is engaged.But I have not yet rewired as I am still kinda thinking things thru.

    What puzzles me is why I not experienced this issue before? Did I just get lucky all those times?
    Click image for larger version

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  • #2
    Would really like some input here from somebody who has a good understanding of the antenna problem. I never did understand this. I thought the basic idea was to avoid "hot" wires "hanging" and not connected to anything but surely you will always have this issue at the pick up selector switch when a pup is not in circuit.

    There is no hum when bridge is in series or parallel mode or when neck alone is cut .So the so I presume disconnecting the screw coil to get the coil cut is somehow causing the issue. As I have said I have used this wiring many on many previous occasions without issues.So am a bit puzzled.

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    • #3
      I'm unable to help with this wiring scheme, sorry. I can only say that this is why I prefer to use separate 3 way switches for series/split/parallel wiring. The dual push pulls always confused me lol.

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      • #4
        I'm assuming that you are using SD pups since you didn't specifically say, but did make reference to the JB.

        That's a very confusing diagram for me. The first thing that I notice is that the bridge pup is either in series oop when the bridge p/p is pulled up/away from the pot (because the red wire is connected to the green wire instead of the white wire), or it's in parallel oop when the bridge p/p is pushed in/down toward the pot and the neck p/p is pulled up/away from the pot. When the neck p/p is pushed in you get bridge pup in split mode. But you've also got the neck black-white coil going to the neck vol pot and also going through the bridge green-red coil to the bridge vol pot. This doesn't make sense to me.

        Is this what you actually want?
        Originally Posted by IanBallard
        Rule of thumb... the more pot you have, the better your tone.

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        • #5
          Tell us exactly what you want your guitar to end up doing and we can help you get there.
          Originally Posted by IanBallard
          Rule of thumb... the more pot you have, the better your tone.

          Comment


          • #6
            I'm having trouble reading the diagram. Those wire colors don't appear to be Duncan wire colors (unless I'm really having more trouble than I think reading the diagram.). Looks like you are shorting out the neck pickup while the bridge pickup is always on; it's not clear if there are additional switches or something to select the pickups. I haven't seen a diagram that looks like this before.

            If you've successfully used this diagram on multiple guitars and only now it's not working, my guess is this time you used different pickups that are wound different than you think.

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            • #7
              +1.
              Originally Posted by IanBallard
              Rule of thumb... the more pot you have, the better your tone.

              Comment


              • #8
                Thank you all for responding. A bit disappointing that nobody actually addressed the issue I was actually inquiring about... that is information about antenna effect which I seem to have got despite having used this wiring before without issue.

                For some reason there appears to be some doubt as to the suitability of the pick ups. In this case the owner of the guitar has chosen Iron Gear.; A very popular brand of budget pick ups in the UK and highly recommended by a very respected local luthier. In this case a Dirty Torque for the bridge and a Blues Engine for the neck . I have this same set in one of my own guitars and it is an excellent all round set, that responds well to this wiring. Although not actually a JB the Dirty Torque is very similar in spec having fibre bobbins slightly over wound with 44AWG enamel wire producing a DC resistance of 16.4 ohms. Magnets are A5.

                I am surprised the actual wiring diagram caused so much confusion among the experts. It is actually quite simple.. I am not claiming originality but it was something I worked out for myself around 8 or 9 years ago wishing to have an alternative to 2 push pulls than just individual coil cuts. And as an alternative to Artie's excellent col cut wiring.The colour code I was using is Iron Gear which is red and green for the screw coil and black and white for the slug coil although I amended the white wire to light blue for clarity.

                The wiring concept is quite simple. A push pull that puts the bridge in parallel with the other rush pull cutting the neck and bridge when it was in one of the 2 modes. Initially I wired it with the coil cut operating when the bridge pup was in series mode by grounding the jumper at the "bottom "of the push pull..But missed the series bridge with cut neck option so amended the wiring to cut in parallel mode by using the push pull to simply disconnect the screw coil ground (green wire) from the circuit.,

                I have been completely unable to follow Guitar Doc's logic regarding the allegations regarding OOP The "reds" on both pups are both wired to the hot side.I would welcome enlightenment.

                Since my original post I have amended the wiring by taking my own advice and adding the jumper in Fig 2 This now connects the green wire from the bridge screw coil to the neck hot (red) when coil cut is engaged instead of leaving it hanging. Rightly or wrongly this seems to have cured the hum as I suspected it would.

                So for some reason I believe I have encountered antenna hum this time despite not having previously had issues with identical wiring. Antenna effect is something about which I have little and probably incorrect knowledge and ,as originally requested, would welcome enlightenment.

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                • #9
                  Info on antenna hum anybody?

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