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How is a "dummy pickup" set up?

Discussion in 'Pickups & Electronics [BG]' started by Flux Jetson, Aug 19, 2012.


  1. I get the basic ethos of the idea, I suppose it is used to "counter wire" a single coil to make a sortof humbucking arrangement. Do I have that right?

    But how it is wired up?

    And how does that differ from the "buck and a half" setup?

    Thanks :)
     
  2. There are several ways to do it. The simplest way would be to run a dummy coil parallel to the audible single coil. This drops the output impedance, however. Some people run the dummy in series with the audible coil. That has the opposite effect in the circuit, of increasing output impedance. (Including inductance.) A more preferable setup, at least theoretically, would include multiple buffered inputs summed to a single output, so that the dummy coil does not load the audible coil. One bass manufacturer does this, but their name escapes me right now. Might be Alembic.
     
  3. Consider this. I'm using separate outputs for each pickup. So any buffering can easily be done "off bass" and in some sort of circuitry built into some sort of enclosure or panel to make it all work.

    http://www.talkbass.com/forum/f8/2-channel-modification-j-many-pictures-908965/

    http://www.talkbass.com/forum/f36/experimental-fully-modular-bass-rig-902681/

    Both of these threads are about the mods I've already done to my Jazz. So with these things in consideration, how might this be done?

    (It's late and my brain has checked out for the night - sorry I'm not more receptive at the moment. Perhaps in the morning when the 5hr Energy has kicked in I'll be able to digest this better).

    Thanks.
     
  4. The dummy coil will need to be on the bass with the audible pickups for the amount of 60Hz hum to remain equal to provide full humcancellation. That being said, you will need three outputs if you want to do the buffering externally. That's really not the best idea, anyway, because then you have to deal with cable capacitance and such before your pickups get buffered. What I would do is buffer the dummy coil and give it two outputs; one to combine with the buffered signal from each pickup. The problem with running a dummy coil away from the bass is that the amount of hum will change as the bass moves around, since the proximity of the pickups to a source of hum will not change equally.
     
  5. I just meant putting the buffers elsewhere. :) Sorry, I should have been more clear.
     

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