Electronics
and wiring,
explained.

The short version

Guitar wiring looks intimidating and it isn't. There are four parts: a pickup, a couple of pots, a capacitor and a switch. Once you know what each one does, every wiring diagram you find online turns from a tangle of lines into something you can actually read.

The numbers, in one place

Part	Value	Why
Pot, single coils	250 kΩ	Rolls off a little treble. Tames bright pickups.
Pot, humbuckers	500 kΩ	Brighter. Humbuckers on 250 k often sound muddy.
Pot, very dark pickups	1 MΩ	Brightest. Can get thin.
Tone cap. Humbucker	0.022 µF	Warm, still musical at full roll off
Tone cap, single coil	0.047 µF	Darker, the classic "woman tone"
Treble bleed resistor	~100 kΩ	Paired with a small cap. Experiment.
Hook up wire	22 to 24 AWG stranded	Lower number = thicker wire
Pot tolerance	Up to ±20%	A "250 k" pot may measure 200 k or 300 k
Multimeter	Cheap, well under the price of a set of strings	You will use it constantly
Mains hum (US)	60 Hz	Sits between a low A♯ and a low B

What electricity actually is

Everything is made of atoms. An atom has three parts:

• Protons. Positive charge
• Neutrons, no charge
• Electrons, negative charge, orbiting the outside

Atoms like to be balanced. Take an electron away and the atom is left positive. Add one and it becomes negative. Either way it now wants to get back to even, so it'll try to grab an electron from a neighbor or push one onto it.

Electricity is that passing of electrons from atom to atom. I think of it like a row of dominoes. Knock the first one over and the fall travels all the way down the line.

Voltage, current and resistance

Think of a garden hose.

• Voltage is the water pressure, the push behind it. Measured in volts.
• Current is how much water actually comes out. Measured in amps.
• Resistance is anything slowing it down. A kink in the hose, or a narrower pipe. Measured in ohms (Ω).

The three are tied together by Ohm's law:

Voltage = Current × Resistance

Know any two and you can work out the third. A guitar deals in tiny amounts of all of them. There's no dangerous voltage anywhere in the instrument, so don't let that part worry you.

How a pickup makes a signal

Magnetism and electricity are two faces of the same thing, and a pickup is where that gets useful.

Every magnet has a north and a south pole. You never get one without the other, and around it sits a magnetic field. That field reaches much further than people expect. A compass will react to a weak magnet from feet away.

Move a coil of wire through a magnetic field and you make electricity in that wire. You get the same result three ways: move the coil, move the magnet, or hold both still and change the shape of the field by moving a piece of metal nearby.

That third one is your guitar.

Inside a pickup

1. Six magnetic pole pieces, usually alnico. Aluminum, nickel and cobalt. All magnetized the same way up
2. Thousands of turns of very fine insulated wire wound around them, typically 5,000 or more
3. Two ends to that coil: a start and a finish. One becomes your hot lead, the other your ground

Pluck a steel string above it and the string's movement distorts the magnetic field. The field moving pushes electrons along the coil. That's your signal, created entirely inside the guitar.

Why pickups get potted

If the coil windings are loose, they can vibrate on their own, from sound in the room, or from the guitar itself. Wire moving in a magnetic field makes a signal, so those vibrations become noise. That's a microphonic pickup, and I've heard it squeal on a loud stage more than once.

Wax potting soaks the coil so nothing can move, which fixes it. Loose metal parts can cause the same problem too, a cover, a spring, so it's worth checking those as well.

It's also why you can sometimes hear tremolo springs through the pickups. The magnetic field extends out of the bottom of the pickup as well, straight through the wood.

What the signal looks like

Hertz (Hz) just means times per second. A string vibrating 110 times a second is 110 Hz, and 110 Hz is your open A string.

Whatever the string does, the electrons in the coil do. Vibrate the string 110 times a second and the current swaps direction 110 times a second. That back and forth is alternating current (AC), as opposed to the one way direct current (DC) in a battery. Everything in a guitar is AC.

Harmonics

A string never produces one clean frequency. Along with the fundamental, 110 Hz on that open A, it produces quiet multiples of it: 220, 330, 440 and on up. Each one is weaker than the last, and the fundamental is both the lowest and the loudest.

On an oscilloscope a single frequency looks like a smooth wave. A real guitar string looks like a jagged, complicated shape, because all those harmonics are stacked on top of each other. Where two waves line up they add together and get louder. Where they oppose each other they cancel out.

That last point matters more than it sounds, because it's the whole basis of the next section.

Hum, and how a humbucker kills it

A pickup is an antenna. It picks up magnetic fields from anything nearby, and the biggest offender is mains power.

In the US the mains alternates at 60 Hz, and every transformer, in a computer, a light, an amp, radiates that 60 Hz field around the room. Your pickup hears it as a low hum. Sixty Hz sits between a low A♯ and a low B, which is why it's such an unpleasant note to have droning underneath you.

Seth Lover's idea

In the 1950s Seth Lover at Gibson worked out the fix. Put a second coil next to the first, and set it up so that:

• Its magnets are the other way up, south where the first is north
• It's wound the opposite way round. The end of one coil connects to the start of the other

Phase, and the wiring options it gives you

Two pickups together can be in phase or out of phase. Out of phase, some of the signal cancels, and you get a thin, hollow, treble heavy sound. Some people want that on tap.

Two ways to flip it:

• Physically, take the magnet out and turn it round
• Electrically, swap which lead is hot and which is ground on one pickup

Series versus parallel

How you join two coils changes the sound as well:

Wiring	How	Result
Series	End of one coil to the start of the next. The two outer ends become your hot and ground.	Louder and thicker. This is how a standard humbucker is wired.
Parallel	Both starts joined as hot, both ends joined as ground.	Brighter and clearer, with a little less output. A useful extra voice.
Out of phase	One coil's connections reversed relative to the other.	Thin, hollow, very quiet. Most of the signal cancels itself.

Series and parallel are both perfectly usable sounds. I think series/parallel switching is often more useful than a coil split, and factory guitars rarely offer it, which is a shame.

Potentiometers

A potentiometer, "pot", is a resistor you can adjust. Inside there are three lugs and a strip of carbon film that acts as a wire with a lot of resistance. A wiper attached to the shaft slides along that film, and the middle lug connects to the wiper.

Put a meter across it and here's what happens:

• Wiper hard over to one side: zero ohms between the wiper and that side, full value to the other
• Wiper in the middle: half the value in each direction

Tolerance

Audio taper or linear taper

• Linear, resistance changes evenly as you turn. Halfway round is halfway in resistance.
• Audio (log), changes slowly at first, then quickly. This matches how your ears actually judge loudness.

Use audio taper for volume. A linear volume pot seems to do nothing until the last part of its travel, and that trips people up constantly. Linear works better for tone, though plenty of people prefer audio there too. Either will function, so don't stress over it.

The volume control

The standard arrangement:

1. Pickup hot to one outer lug
2. Wiper (middle lug) to the output
3. Other outer lug to ground
4. The metal back of the pot also goes to ground

Now the signal arrives and finds two paths, one to ground, one to the output. The wiper decides how the resistance is split between them, so it acts as a voltage divider:

• Turned down: the path to ground has almost no resistance, so nearly everything takes that shortcut. Silence.
• Halfway: resistance is even both ways, so roughly half the signal reaches the amp.
• Turned up: the path to the output has almost no resistance. Full volume.

Capacitors

A capacitor is a very small rechargeable battery. Two metal plates with an insulating layer between them. Apply power and one plate goes positive, the other negative, and it holds that charge briefly after you disconnect it.

The useful part:

Capacitance is measured in farads, but a farad is enormous. Guitars use microfarads (µF), 0.022 and 0.047 being the two you'll meet.

The value decides which frequencies get through. A capacitor takes a moment to swap its charge over, and that moment is what lets fast (high) frequencies through while blocking slow (low) ones.

The tone control

A tone knob is a low pass filter. It lets the lows pass to the amp and sends the highs to ground.

The wiring:

1. Signal into one outer lug
2. Wiper out to the capacitor
3. Capacitor to ground
4. Third lug unused

Turn the knob and you change how much resistance stands between the signal and that capacitor. Wide open, there's a lot of resistance and almost nothing escapes. Rolled off, the resistance drops away and the high frequencies pour through the cap to ground, leaving you the lows.

A bigger capacitor dumps more treble, so it sounds darker at full roll off. A higher value pot leaks less treble when the tone is up full.

Treble bleed

Turn a volume knob down and you lose treble along with the level. The guitar goes dull as well as quiet. A treble bleed lets the highs past the volume pot so the tone stays consistent.

All three versions fit across the volume pot's input and output lugs:

1. Capacitor alone
2. Capacitor with a resistor in parallel, around 100 kΩ
3. Capacitor and resistor in series with each other

Each behaves differently, and so does each combination of values. Buy a few caps and a few resistors and try combinations. This is genuinely a case where the right answer is whichever one you like, not whatever a forum tells you to use.

Whether you want one at all depends on you. Plenty of players use the volume knob as a tone control on purpose, and there's nothing wrong with that either.

Switches

Switches are described by poles and throws:

• Poles, how many separate circuits the switch controls
• Throws, how many positions each one can connect to

A light switch is SPST, single pole, single throw. On or off.

A DPDT is double pole, double throw. It has six lugs in two rows of three. The middle lug in each row is the "common". Flick the switch and each common connects to the lug on one side or the other. The two rows are completely independent, which is what makes a DPDT so useful. You're flipping two separate connections at once.

You'll also see switches described as on on, on off on or on on off. That tells you what happens in each physical position, including whether there's a dead middle.

What DPDT lets you do

Because it swaps two connections simultaneously, one DPDT can:

• Reverse phase, swap which pickup lead is hot and which is ground
• Split a coil. Ground the junction between the two coils, silencing one
• Switch series to parallel

Selector switches

A Gibson style three way toggle has three lugs and a ground tab. Each pickup's hot goes to an outer lug, the common goes to your volume, and the middle position connects both.

A Fender style blade switch works the same way with more positions and more lugs. Some have extra poles for more complex wiring.

Coil splitting and push pull pots

A push pull pot is just a normal pot with a DPDT switch glued to the bottom of it. The two halves are completely separate. The pot does its job, the switch does another.

To split a humbucker, take the two wires that are normally joined together in the middle of the pickup (on a four conductor pickup these are usually the ones you'd tape off) and run them to the switch. In one position they stay joined and the pickup behaves normally. In the other, the switch sends that junction to ground, which short circuits one coil and leaves you with the other.

You only need one half of a DPDT for this, so a single pole switch would do.

Kill switch

A momentary switch that cuts the sound while you hold it. Two ways to build it:

• Break the signal, an on off momentary switch in the signal path. Normally closed; pressing it opens the circuit.
• Short to ground, an off on momentary switch from the hot to ground. Normally open; pressing it sends the signal straight to ground.

Both work. Some builders add a small capacitor or resistor to soften the click you get on switching, which is fairly inherent to the design.

Grounding and shielding

Every piece of metal in the guitar should be grounded: pots, switches, jack, bridge. Your tuners get there through the strings once the bridge is grounded.

For a hard tail bridge, drill a small hole from the control cavity through to under the bridge and run a wire. Once the bridge is grounded, touching the strings grounds you, which is why the hum often drops when you put your hand on them.

Shielding

Line the control and pickup cavities with copper tape, connect it all together, and run a wire to ground. Do the back of the pickguard too. That creates a Faraday cage: incoming radio interference hits the shield and goes to ground instead of reaching your pickups.

Conductive paint does the same job, with one catch: you can't solder to it. Attach the wire with a screw and a washer instead.

Shielding matters most with single coils. Humbuckers already reject a lot of interference, so it's less critical there, though I never call it a waste of time.

Hookup wire, and the myths attached to it

There is more nonsense sold about guitar wire than about almost any other part, so let me put the whole thing in perspective before we get to what to actually buy.

Why gauge barely matters here

Look at what your pickup is actually putting out. A few hundred millivolts on a hard strum, and a current so small it is measured in millionths of an amp. Now think about how far that signal has to travel inside the guitar. A few inches. Maybe a foot if you take the scenic route around the control cavity.

A tiny signal going a few inches does not need heavy wire. It is nowhere near the current that would make thickness matter. Running fat wire in a control cavity is like running a fire hose to fill a shot glass. It does no harm, it just does nothing for you, and it is stiffer to work with and harder to get neatly into a cramped cavity.

What gauge actually changes is resistance, and over these distances that difference is so small it disappears next to the pickup itself, which is sitting there at several thousand ohms. Your pot values, your cap, your cable and your pickup are doing all the work. The hookup wire is a rounding error.

There is no such thing as magic vintage wire

You will see wire sold as vintage, or vintage spec, at many times the price of ordinary wire, with claims about warmth or sweetness or the way they used to do it. It is marketing. Copper from 1958 and copper from this year conduct the same way, because copper is copper. Nothing about the decade a spool was made in changes the physics.

What was genuinely different back then was the insulation and the manufacturing, not the conductor. So the honest reason to buy cloth covered wire is that you want a vintage correct look in the cavity, or you are restoring an old instrument and you want it to look right when somebody opens it up. That is a perfectly good reason. Just do not pay a premium expecting to hear it, because you will not.

Insulation is insulation

Same story here. Cloth, PVC, PTFE, rubber, they are all non conductive, and being non conductive is the whole job. The insulation keeps the signal in the wire and keeps two conductors that should not touch from touching. It is not in the signal path at all, so it cannot be adding or subtracting anything from your tone.

Where insulation types actually differ is in how they behave under a soldering iron and in your hands:

• PVC is cheap and everywhere, and it shrinks back from heat if you linger with the iron.
• PTFE shrugs off soldering heat and is the easiest to work with if you are slow or still learning.
• Cloth over a plastic core is the vintage look, and it strips a little differently because you are pushing the braid back rather than cutting a jacket.

Pick on heat tolerance and on how it feels to work with, not on tone.

So what wire is best

Copper, stranded, somewhere in the 22 to 24 AWG range. That is the answer, and here is the reasoning behind each part of it, because the reasoning is what lets you make the call yourself next time.

Copper over aluminum. Copper conducts better for a given thickness, so you need less of it, and more importantly it solders easily and reliably. Aluminum is a nuisance to solder, it grows an oxide layer almost instantly that fights the joint, and it is more brittle, so it does not love being bent into a tight cavity or flexed when you take the control plate off. It gets used in house wiring where cost and weight over long runs matter. Neither of those is your problem inside a guitar. Buy copper, ideally tinned copper, which solders even more easily and does not tarnish on you.

Stranded over solid. This one is about the environment the wire lives in. A guitar vibrates constantly, gets knocked around, travels, and gets opened up whenever something needs changing. Solid core wire work hardens when you flex it, and eventually it snaps, usually right where it enters a solder joint, which is the most annoying possible place. Stranded wire is many fine strands twisted together, so it bends and takes vibration without fatiguing. Solid core has its uses, mostly where a wire needs to hold a shape, but in a control cavity stranded is what you want.

The gauge range. 22 to 24 AWG is the practical sweet spot, and remember the numbering runs backwards, so the lower number is the thicker wire. Much thinner than that and it gets fragile and fiddly to solder. Much thicker and you are fighting stiff wire in a cramped cavity for no electrical benefit. 26 AWG will work fine electrically, it is just thin enough to be delicate.

Buy decent wire, buy enough of it, and spend the money you saved on wire that was never going to sound different on a good soldering iron instead. That will improve your results far more than any spool ever will.

Parts

On capacitors: a good one is genuinely cheap. There is no reason to buy the absolute cheapest one you can find, and no reason to buy the expensive boutique one either. Buy a decent film cap with a tight tolerance and move on.

Your most useful tool

A digital multimeter that can measure resistance, voltage and continuity. It's cheap, and it's not optional.

You'll use it constantly:

• Continuity to work out which lug on a switch is which, and to confirm your shielding is all connected
• Resistance to check pot values against what's printed on them
• To find the grounded side of an output jack. On a barrel jack, the outer part is always ground

One more thing worth knowing

If an old guitar crackles when you turn a knob, the wiper inside the pot is dirty. Electronic contact cleaner sprayed into the opening will clean and lubricate it, and it usually clears the noise up completely. It's a two minute fix that people replace pots over, and that's money they didn't need to spend.