250k volume coil split mod, retains 500k for humbuckers [diagram included]

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Alex C
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250k volume coil split mod, retains 500k for humbuckers [diagram included]

Postby Alex C » Sat Apr 01, 2017 3:00 pm

I'm the proud owner of a DC727 that I received about two years ago (with the customary "order on the way" and "NGD, pics!" posts at the time), and I've been very pleased with it. I ordered it just before the Lithium pickups were available, but I was able to get a late prototype version of them, which I'm also pleased with and which are still in this guitar even though I have a Crunchlab/Liquifire set laying around.

I ordered the guitar with individual coil-split toggle switches, and my only minor issue has been that the split single coil sounds can be a bit harsh in the upper mids and treble frequencies because the 500k volume pot is still in place when the coils are split (whereas most single-coil setups use a 250k volume pot, which rolls off some of that high end). To address this, I came up with the following modification.

The spare pole on each DPDT coil split toggle is used to switch in a fixed 470k resistor to ground at the output of each pickup, so that when a split pickup is selected the 500k volume pot has a ~500k resistor in parallel with it, which is roughly equivalent to a 250k pot. When a pickup is not split, the 470k resistor is not connected, so in humbucking mode the 500k pot is retained. Below is a diagram illustrating this.


This has really smoothed out some of the "bright honk" and "bite" of the split-coil sounds, making them a bit more Strat/Tele-like, and I can now switch seamlessly from humbucker to single coil mode without adjusting the guitar's tone control or the amp EQ.

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Re: 250k volume coil split mod, retains 500k for humbuckers [diagram included]

Postby UnexplodedCow » Fri Apr 21, 2017 9:00 am

Good idea, though I can also see it being approached with a 500K resistor between the center and left lugs on the pot, changing the taper of the pot when rolling volume down (it would act like a 250k).

Outside of that, I don't use coil splitting very much, and prefer parallel wiring, with series for that extra kick.
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