I completed the pickup surgery on my EB-0 today. It now sports a mudbucker with four output wires - a pair for each coil - making it possible to create different coil combinations, each with some unique sound characteristics. I built a new wiring harness to allow series/parallel switching of the humbucker coils, and also coil-tap for running it in single-coil mode.
The coils in a stock mudbucker are hardwired in series. My pickup had a reasonable amount of slack in the wires coming out of the coils. Not sure if they are all like that, but this was a welcome suprise, and made the job fairly simple. Here's a shot of the pickup once I carefully extracted the wires out from under the coils:
In order to perform this mod, I had to run a four-conductor wire to the pickup. I chose to use some shielded cable that I had handy, and I grounded the shield to the pickup casing. I also ran a wire (not pictured) up to the pickup cover to ground it and keep it from buzzing when touched (I think I need to do that to my EB-3 too - buzzes like the dickens). Here are some shots of the 4-wire mud, before I tucked the extra slack back under the coils:
In order to accomplish all of the switching permutations, I used two push/pull pots in the following configuration:
The volume pot switches between humbucking and single-coil mode, and the tone pot's switch changes the relationship of the pickup coils from series to parallel wiring. This has a marked effect on the impedance and sound of the pickup. In normal series-mode, the pickup measured about 30K. Single-coil mode cuts that in half, and parallel-mode drops the impedance down to about 7.5K.
The most difficult part of this whole thing wasn't splitting the pickup coils - it was fitting those pots in the control cavity. I couldn't get the cover back on because the pots are so tall! I ended up taking out the brass shield insert and sanding down a couple of high spots in the wood. Barely got everything to fit! This is the finished product:
(Dig my super rare capacitor too. I'll have it paid off next year. It's totally vintage - out of a sweet '68 Teisco.
)
So hows it all sound? Well- the differences between the various settings are subtle, but were immediately obvious to me. As you drop to single-coil and parallel mode, the characteristic mud washes away, and the sound becomes more clear, and less "saturated". I made a clip to
try and demonstrate the differences:
The clip just repeats the same passage, iterating thru the following settings:
1. Stock mudbucker w/coils in series
2. Coils in parallel
3. Single coil
4. Single coil w/tone rolled off
5. Stock mud w/tone rolled off a bit
I tried to record that as raw as possible. It's just bass -> Alembic preamp (set flat) -> computer. You probably need to listen thru phones or some decent monitors to fully appreciate the subtle differences in tone.