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mm wiring help

Discussion in 'Pickups & Electronics [BG]' started by abemo, Nov 30, 2012.

  1. abemo


    Feb 27, 2012
    Arvada, co
    So here's my plan:

    I have a jazz bass that just doesn't do it for me anymore. I don't know how else to say it. So I'm thinking of expanding the routes to accommodate a hh style pickup configuration, and i'd like to do this for wiring: 2 series/single mini toggles (1 per pup), 2 mini toggle killswitches (again, 1 per pup), V, V, and 1 diode knob for jace bruce style passive distortion.

    My two questions are:

    1. How do I isolate the two killswitches from the rest of the circuit? It seems that if I hit one killswitch it would ground both pups, is this possible without a preamp?

    2. With the diode knob, i'd like it to only effect the bridge pup, so I could blend a fully clean signal from the neck pup with the distorted signal from the bridge. Again, is this possible without a preamp?

    Thanks in advance
  2. I'll draw a diagram if you want it. There are two ways to do this; independent volumes, or volumes that do not cause a variable impedance loading effect. Also, which coils did you want to split to? Inner, outer, north or south? And why not series/single coil/parallel or north coil/series/south coil switches?

    They are wired like volume pots in a VVT circuit. The common either connects the hot to the output or ground.

    Not possible without either buffering or adding resistors to prevent the pickups from running parallel. This will kill output.
  3. abemo


    Feb 27, 2012
    Arvada, co
    Basically I want the options of the humbuckers in series, or run it like a jazz bass, with two single coils at opposing polarity. The diode idea was to be able to give myself a clean/dirty mix directly off the bass.

    As far as the killswitch, I've done them before, I usually do a basic on/off going between the hot an ground to keep the cable loaded, would I get feedback if they were wired as a straight disconnect?
  4. SirMjac28

    SirMjac28 Patiently Waiting For The Next British Invasion

    Aug 25, 2010
    The Great Midwest
  5. As I said, there are four ways to do series/single coil switching in this case. Inner, outer, north-only and south-only.

    Feedback is caused by running the output of something back into its input. That is not a concern unless you were using a bass to control a source of 60Hz hum. Simply disconnecting the output of a bass with a killswitch is never a good idea, however, as it leaves an infinite impedance, which may give you a lot of hum. Outputs are traditionally shorted, but what you are doing is two on/off switches rather than a killswitch. That means you either place the switches before the volume pots, and short the pickups rather than the outputs, if you have independent volumes; or you place the switches after the volume pots if you want the volumes wired to vary output impedance, but add a resistor of some finite value parallel to the output so there will be no hum when both pickups are off. The switches would be wired to short their inputs rather than their output, in this case, as well.
  6. abemo


    Feb 27, 2012
    Arvada, co
    Ok, so I'm thinking that the easiest way to do it would be pup-mute switch (shorts out pup)-single/series switch (shorts outer coil, as i'd like to go with the inner coils for single mode)-V-output for each pup? Am I understanding this correctly? Thanks for the help.
  7. I say go for it. If you want to do it for a project, something to do and something unique. By all means. Just please realize that most of the MM sound is in the active preamp.

    I have a Precision bass that I routed out and added a Musicman pup at the bridge with passive Duncan SPB3 P-pups and a SMB4a pup.

    The SMB4a alone is not as impressive sounding as it looks. It took some experimentation to get it sounding a way I like. Now I have the P-pup and both coils of the MM pup wired up in series with each other. This gives me what I would consider to be a usable sound.
  8. abemo


    Feb 27, 2012
    Arvada, co
    And that's a lot of why I want to keep the single/single jazz style option on it, but I play tested several mm style passive basses, especially with double humbuckers, and overall I've been impressed. I don't think the bridge humbucker solo is a great option, but add the neck humbucker in series and it comes alive, and brings out the missing lows and punchiness that the preamp usually has to add. Plus, I'll have a few more options with humbucker/single configs and whatnot.