DIY workshop: adding coil-splitting to humbuckers with push-pull pots
If you’ve got a humbucker-equipped guitar, you might miss the spanky, bright sounds of single-coil pickups – but worry not! One of the easiest mods you can do is adding a coil-split via a push-pull pot. Ready to unlock some extra sounds? Grab your soldering iron and wire strippers, and let’s dive in.
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Well, actually – a quick note before we get to the edge of the diving board: to do this, you’ll need humbuckers with modern four-conductor wiring. Some humbuckers will have two-conductor wiring, either in the form of modern insulated multi-core, or vintage-style braided wiring. Four-conductor wiring will have an extra pair of wires that, when the pickup is in humbucker mode, are simply connected and taped off – these are the wires that will allow us to perform the coil-split.
So the first thing to do is to pop the pickguard/control cover off, take a look at your guitar’s wiring and check that your humbuckers are four-conductor. If they’re not, you can either mod your pickups (a little risky and difficult, and beyond the scope of this guide!) or swap out for pickups that do have this wiring.
To understand why we need four conductor wiring, and help us down the line if anything goes wrong, let’s look a little deeper at how a humbucker works. A standard humbucker consists of two coils, commonly called the north coil and the south coil. These are wound in opposite directions around pole-pieces magnetised with the opposite polarity. Standard humbucker operation calls for the finish wraps of each coil to be wired together, and the start of wrap of the south coil connected to ground. The start wrap of the north coil will then carry the signal picked up from the strings.
This is what makes a humbucker, well, buck the hum: because of the opposite winding and polarity of each coil, they pick up the same polarity of signal from the moving strings, but pick up opposite-polarity versions of any hum. Combining the two signals, then, means that you both get a beefier sound from the strings and cancel out the noise at the same time.
For coil-splitting, we obviously want to isolate just one of the humbucker’s coils, ignoring this hum-cancelling behaviour but getting a sound much closer to a traditional single-coil. To do this, we can take those two finish wraps, and wire them to ground, along with the start wrap of the south coil. This means that any signal generated in the south coil just gets conducted away to ground – but we still read the north coil’s signal as normal.
What do you need to perform this mod?
Alongside compatible pickups, you’ll also need a few tools and supplies to make this job go smoothly. Most obviously, you’ll want the push-pull pots themselves – I’m using CTS pots here, and I’d recommend them – if you’re going to the trouble of taking your guitar apart and rewiring it, you might as well put nice and reliable high-quality full-sized pots in there, especially with push-pull pots, which have more moving parts. Just keep in mind you may need to drill out the potentiometer hole a little larger if you’re currently using mini pots.
You’ll also want some of your hookup wire of choice, as you’ll need to make a few new connections, and it’s good to have flexibility rather than just rely on re-using what’s already there. To get that in place you’ll need a decent soldering iron, solder itself, wire strippers that will accommodate the full multi-core pickup wire, and a multimeter. These are, in general, pretty essential for general maintenance, repairs, testing and troubleshooting, so if you plan to keep your guitars operational yourself rather than take them to a tech, then they’re a worthwhile investment.
Wiring up a push-pull pot
CTS push-pull pots come with a little PCB that breaks out the standard switch into separate connections – here’s how they change depending on whether they’re down or up:
These pots are being visualised as if you’re working on an upside-down guitar.
As you can see above, we have two common connections, each of which switches between two poles depending on the pot’s position. (It’s worth noting here that a push-pull pot is two components in one – the push-pull switch doesn’t interact with the potentiometer). If we want, as is conventional, to have the coil split when the pot is pulled up, all we need to do is twist the two finish wraps together and wire them to either of the common connections – and then wire connection 1 or 3 (depending on the common connection we used).
For my project, I’m splitting the humbuckers of a Squier Telecaster Deluxe. The wiring scheme here is, in a very Gibson manner, two volumes, two tones and a three-way toggle switch – I’m replacing each pickup’s volume control with a push-pull pot to split each individually. The full wiring for the guitar essentially remains the same as standard, but each pickup has its finish wraps wired like this (or with the finishes to C1 and ground to 1):
Just for clarity I’ve used Seymour Duncan’s colour scheme here for the wire colours.
There are a few tricks to achieve this in practicality. First things first – identify how things are already wired, as different pickup manufacturers will colour-code their wires differently. Two of the four conductors will be soldered together and taped off – these are our finish wraps. Another will be going to a lug on the volume pot – this is the north start, or hot wire of the pickup. And finally there’ll be a wire that’s connected to both the shield of the multi-core and a ground connection, like the back of the pot.
Wires identified, it’s time to desolder and remove the pots you want to replace with push-pull. There’s no hard-and-fast rule as to which pots to replace – you can put the push-pull controls on the tone pots if you want, or use both sides of a single push-pull to split both of your pickups at once. You could even use switches rather than pots if you’d rather – the same principle applies. Ground the finish wires, and you split the pot.
Once you’re ready to reinstall, get your pots in position and get your pickup wires ready to work with. You can use your wire strippers to remove the main insulation for a bit more to work with, and you’ll also want to make sure the ends of the core wires are nice and clean to work with. You can strip, twist and tin the two finish wraps together to make it easier to wire them both to the push-pull, and do the same for the south start and the shield.
The rest of the wiring goes like any other wiring job – here’s how I did my Telecaster Deluxe in the end (switch, output jack and string ground not shown, as those will vary between guitar):
You don’t have to follow this exactly – there are loads of wiring schemes out there depending on your guitar and your goals. The main thing is that those finish wraps connect to ground when you want a split-coil sound, and are only connected to each other when you don’t.
Wired up, it’s time to test. You can test your wiring before stringing up your guitar in a few ways – for basic operation, the old screwdriver test is quick and easy. Simply plug your output jack into an amp (carefully, depending on how detached from your guitar the pickguard is!) and lightly tap on the pickups with a screwdriver. You can then go through the switch positions to check that the bridge makes a noise and the neck doesn’t when the switch is down, and so on – and you can also test the volume and tone controls here.
To test that the splitting has been a success, you can also just listen for an increase in hum when you pull up the pots for single-coil mode – but, let’s be a little more rigorous, and get out the multimeter. Measuring between the sleeve and the tip of the output jack with your multimeter on the 20K Ohms setting, you should read the total impedance of the selected pickup. For a humbucker this varies, but it’ll likely be between 6K and 9K ohms. If you pull the pot and the impedance decreases by half, then you’ve successfully split!
Now you can enjoy both full-bore humbucker sounds and single-coil sounds at the pull of a pot. Get that pickguard/control cover back on, and get playing.
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