Dummy Coils for Dummies

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Yesterday I rolled a dummy coil for my Jazzmaster in an attempt to tame some of the noise the 2 singlecoils pickup.

I followed the guidelines from this very informative article:

https://sites.google.com/site/stringsandfrets/Home/noise-reduction-for-sc-pickups

The principle in short is as follows:

To cancel the noise of your real pickup, connect a dummy coil (without magnets) that senses the same amount of noise, in series out of phase. If you have a dummy that is identical to your real pickup in terms of area and number of turns, the noise cancellation will be optimal. But the increased resistance and the changed inductance will impact and change the tone of your pickup.

One way you can counter that is to create a dummy that is larger than the real pickup and reduce the number of turns. The number of turns needed to sense the same amount of noise is reduced proportionally by the increased area of the coil. I have seen differing versions online of how the relation between number of turns / area is.

Example: increasing the area inside a coil by a factor of ten and decreasing the number of turns in the coil by a factor of ten

VS: increasing the area inside a coil by a factor of ten and decreasing the number of turns in the coil by a factor of 100

The latter was how it was explained in http://www.google.com/patents/US20050204905 which I understood is the patent for the Suhr backplate dummy coil system, so I decided to follow that route  and see how it goes.

My pickups are wound to about 9000 turns. I guesstimated I could fit a dummy coil about twice the area of the real pickup in the cavity under the pickup selector switch. I wound the dummy to 2250 turns with AWG38 wire to reduce the resistance. The finished coil had about 1.5k resistance.

On my Jazzmaster, the upper control plate sported 3 switches, one for series/parallel, one for phase of the neck pickup, one for adding a cap in series to cut lows. I decided to replace the whole wiring, leaving these switches unused (for now..) and replacing the pickup selector toggle switch with a 3p4t rotary switch that allows 4 pickup combinations:

Bridge alone + Dummy

Neck alone + Dummy

Bridge and neck series, no Dummy

Bridge and neck parallel, no Dummy

The only thing you need to check once you have wired everything together is whether in the positions 1 and 2 you have noise cancelling or noise addition. If you have more noise, just flip the leads of the dummy coil around.

Here is my wiring schematic:

Jazzmaster dummyTo my amazement, the dummy coil did indeed cut out most of the annoying noise, at least as much as did the series / parallel positions.

I can finally go crazy and stack multiple fuzzes and distortions together  😀