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What is the definition of Coil Tapping and Coil Splitting?

What is coil tapping?

Most of the time when someone says “coil tap,” they are actually referring a coil split. Actual coil tapping is remarkably rare these days.

The idea with a coil tap is when winding a single coil pickup, you stop the winder part way through the winding process, attach a new lead wire directly to the magnet coil wire at that spot, then continue winding; this new lead wire is the “tap” for your single coil pickup, giving you access to multiple pickup impedances. Les Paul went crazy with this idea. His “recording guitar” and low end counterpart “Triumph” bass had pickups that where “impedance variable” accomplished through the use of multiple coil taps on each coil and a rotary selector switch.

What is coil splitting?

Coil splitting most commonly refers to dual coil pickups, but four-coil quad-coil pickups can be split as well. This basically means you are shutting half of the pickup off. If you have a dual-coil and split, you get a true single coil. If you have a quad-coil and split, you are left with a humbucking dual-coil.

Can a “split-coil” pickup be split?

No.

As counterintuitive as it might seem, a “split-coil” pickup cannot be split. A split-coil pickup is where you have two shorter coils that each cover only half of the strings. On a 4 string bass, one coil senses the E (4) and A (3) string, while the other handles the D (2) and G (1).

If you were to turn off half of a split-coil pickup, you would “lose” two of those strings. A classic example of a split-coil configuration is the Fender Precision Bass, but there are also many humbucking Jazz bass split-coil pickups. Despite all of these designs being dual-coil, they cannot be split.

There are two types of coil splitting?

We have established that you have to start with dual or quad-coil humbucking pickup to be able to implement a coil split. There are essentially two completely and fundamentally different ways it could be accomplished.

Some humbuckers are wired in series and some are wired in parallel, and coil split wiring for each of them is different.

Type 1: Series humbucking / Split single-coil

This is the more common type. The vast majority of humbuckers are designed for and are typically used in series operation; it is fairly easy to spot inside a control cavity.

Humbuckers are typically four-conductor wiring, and that gives you access to both sides of each coil.

When a humbucker is wired in series it means the two of the four conductors are soldered together and to nothing else. Typically, this connection is insulated with a piece of heat shrink tubing; this is the series link of the two coils.

Many humbuckers ship from their factories with this connection already made as a courtesy indication of which two wires should be linked for series. However, not all pickup manufacturers use the same color coding, so this is actually valuable information.

Most of the time when we coil split a series humbucker, what we are doing is taking that heat shrink tubing off and both of the wires in the series link and that gets wired into a toggle switch or push pull pot. The switch connects (or doesn’t connect) the series link to ground, which shorts out the bridge coil and enables the neck coil.

There is also an alternate version of this wiring that enables bridge coil and disables the neck coil instead.

Type 2: Parallel humbucking / Split single-coil

Some examples of factory wired parallel humbuckers would be a traditional Music Man pickup and some of the other dual coil designs made by Nordstrand and Aero.

More than a few pickup companies actually make alternate series and parallel versions of particular pickups. It is important to note that despite the fact that the four-conductor wiring gives you option to wire a humbucker in either fashion, each pickup is designed with one or the other in mind, and generally sound better when you stick with the designer’s plan for it.

If you are wiring a humbucker for parallel and the manufacturer has made the courtesy “series link” connection, that connection needs to get broken apart. At this point one of the two wires previously used in the series link becomes a separate output wire for its coil, and the other gets grounded. Now each coil has its own output, and one output wire goes direct to signal, while the other is brought to a switch or push-pull pot where the switch then connects (or doesn’t connect) this output wire to signal, which is usually the blend pot, but wherever the other output wire goes next is where this goes too.

FAQ section

“This sounds very complicated. Will you perform the work for me?”

No, because it would require physically being at your workbench to help you that much, and we probably don’t live in the same place.

“What about Mike Pope Flexcore preamp systems, as they seem to offer an integrated coil split and they are calling it a coil tap?

Mike calls it a “tap” despite the fact that “coil-split” would fit more conveniently into our glossary. He is talking about a coil split, and is VERY IMPORTANT to note that it is configured as a parallel humbucking to single-coil type. This is because the flexcore was designed with Fodera Instruments in mind which are always set up as parallel/split. It is very nicely integrated into his preamp system. It makes it easy as there are no soldered connections.

Unfortunately, it does not help you very much if you desire the series/split type of functionality. If you want a series humbucker and a split coil you will have to wire a traditional soldered connection switch in front of the preamp, the same as you would for any other brand of preamp. If you want parallel humbucking and split order his “coil tap” switch, but only order 1 of them, as only one is supported by the system, and affects both pickups simultaneously. If you want separate parallel humbucking/split switches for each pickup you will have to wire that up yourself with the hardwired soldered switches.

“How would I perform the work myself?”

When looking at the diagrams, remember that everywhere marked as “ground” means you need to tie that into the grounding system of the instrument. Usually, this means the back of a potentiometer, but it is just as common to be dealing with potentiometers on bodies that cannot be soldered to because they are made of plastic. In that case, you will need to find other ways to sum all the grounds together. There are grounding strategies out there, such as “star grounding,” but for most practical purposes, ground is ground. Just make sure that all “grounds” are interconnected together someway somehow. Where it is marked “output,” that means off to the next thing in the signal chain. Most typically will be the one of the two center tabs of your blend control, or the center tab on a volume control in a dual volume system.

Important note: Every manufacturer uses a different color coding for wiring. Consult the documentation for proper color coding for your particular brand pickups.

Have more questions? Email us at sales@bestbassgear.com and we will do our best to answer.

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