Electronics
How pickups work.
There is more nonsense talked about pickups than about any other part of a guitar. So here is what is actually happening in there, why position changes the sound so much, what a humbucker is really doing, and which of the numbers on the spec sheet are worth anything.
I hold a granted US patent on a pickup design, a fully passive variable inductance pickup, US 9,165,545. It has since been cited as prior art in several later Fender patents. I mention it only so you know the following is coming from someone who has had to make this work on paper and on the bench, rather than repeat what a forum said.
The short version
A pickup is a magnet with a lot of very fine wire wound around it. That is the entire device. Everything else is refinement.
It is not a microphone. It has no idea what your guitar sounds like in the room. What it does is sense a piece of steel moving inside a magnetic field, and turn that movement into a voltage. Nothing else in the room exists as far as it is concerned.
Once that clicks, a great deal of pickup mythology falls apart on its own.
The mechanism, properly
Here is the chain, in order:
- The magnet in the pickup magnetises the section of string sitting above it. That piece of your string is now, in effect, a small moving magnet.
- You pluck the string and it vibrates.
- That moving magnetised steel changes the magnetic field passing through the coil below it.
- A changing magnetic field through a coil of wire induces a voltage in that wire. This is basic electromagnetic induction, and it is the whole trick.
- That voltage, alternating in step with the string's vibration, runs out of your jack and into the amp.
Two consequences fall straight out of that, and both surprise people.
The string has to be magnetic. Put nylon strings on an electric with standard pickups and you get silence, because there is nothing for the magnet to act on. Pure bronze acoustic strings behave badly on magnetic pickups for the same reason. This is also why your low strings, with more steel mass, tend to come through louder than the plain high ones.
The pickup only senses the string directly above it. It is sampling the string's motion at one specific point along its length. Hold that thought, because it explains the next section entirely.
Why neck and bridge pickups sound so different
This is the part that gets explained badly everywhere, usually with words like warm and woody, when the actual reason is simple geometry.
A vibrating string does not move the same amount along its whole length. It is anchored at both ends, so it barely moves at the bridge and at the nut, and it swings widest around the middle of its length, which is up near the twelfth fret.
| Position | What the string is doing there | What you hear |
|---|---|---|
| Neck pickup | Sitting near the widest part of the swing | More output, stronger fundamental, fuller and rounder |
| Bridge pickup | Sitting where the string barely moves | Less output, proportionally more high harmonic content, brighter and thinner |
You could fit the exact same pickup in both positions and they would still sound different, because you are sampling the string in two places where it is doing two different things. Manufacturers then compensate by winding bridge pickups hotter to even up the volume, which adds its own colour on top, but the underlying difference is position, not the part.
This is also why a 24 fret neck changes the neck pickup's character. It is not that some sweet spot has been violated. The pickup simply has to sit further back from the widest swing point, so it behaves a little more like a middle pickup.
Single coil and humbucker, what is actually different
The single coil
One coil, wound around magnetic pole pieces. It is direct, detailed and open sounding, and it has one well known problem: a coil of wire is an excellent antenna. It happily picks up the electromagnetic noise radiating from mains wiring, lighting dimmers, computer screens and transformers, and delivers it to your amp as hum.
The humbucker, and why it cancels hum
Two coils, side by side, and here is the trick that makes it work:
- The two coils are wound in opposite directions.
- Their magnets are set with opposite polarity.
Now follow what happens to each kind of signal.
Hum arrives from outside and hits both coils essentially the same way. Because the coils are wired in opposition, that identical noise appears with opposite sign in each and cancels when they are summed. The hum is gone.
The string signal gets flipped twice, once by the reversed winding and once by the reversed magnet. Two flips put it back the way it started, so instead of cancelling, the two coils add together.
Noise cancels, signal adds. Everything else people attribute to humbuckers is a side effect of that arrangement rather than the goal of it.
Why humbuckers sound darker, which is not about output
The two coils sit a small distance apart, which means they are sampling the string at two different points. Those two samples are slightly out of step with each other.
For long wavelengths, the low fundamentals, the difference is negligible and they reinforce. For short wavelengths, the high harmonics, the two samples can arrive out of phase and partially cancel each other.
So a humbucker quietly loses some top end as a direct consequence of having two spaced coils. That is the real reason for the thicker, rounder character, and it would happen even if the pickup were not wound hot at all.
The numbers on the spec sheet, and which ones lie
DC resistance, the number everybody quotes
Almost every pickup is advertised with a DC resistance in kilohms, and buyers treat it as a tone rating. It is close to useless for that.
It does not tell you the wire gauge, the magnet type, the coil geometry, or how the thing is going to sound. Two pickups can measure the same and sound nothing like each other, because you can reach the same resistance with a lot of thin wire or less thick wire, wound tall and narrow or wide and flat, over completely different magnets.
Inductance, the number that actually matters
What genuinely shapes a pickup's voice is its inductance, working together with the capacitance of your cable and the loading of your volume and tone pots. Together they form a resonant circuit with a peak, and where that peak sits, and how sharp it is, is what your ear identifies as the character of the pickup.
- Higher inductance, which generally means more turns of wire, pushes that resonant peak down in frequency. The result reads as darker, thicker, more compressed.
- Lower inductance puts the peak higher up, which reads as brighter, more open, more detailed.
This is the reason a very high output pickup is usually a darker pickup. You cannot pile on turns to get more voltage without also raising inductance and dragging the resonance down with it. Output and brightness are traded against each other, and that trade is a physical constraint, not a design preference.
It is also the property my own patent is built around. If you can vary the effective inductance, you can move that resonant peak deliberately rather than being stuck with wherever the winding left it.
Magnets
| Magnet | Character | Note |
|---|---|---|
| Alnico 2 | Softer attack, sweeter, less output | Weaker field means less pull on the string |
| Alnico 3 | Weakest of the common alnicos, very open | Least string pull of the set |
| Alnico 5 | Tighter, punchier, more output | The most common choice by far |
| Alnico 8 and ceramic | Strongest field, highest output, hardest attack | Most string pull, watch your height |
The practical thing to take from that table is not which magnet sounds best, it is that stronger magnets pull harder on your strings, and that pull has consequences you can hear.
Pickup height, the free adjustment nobody uses
Moving a pickup closer to the strings puts it in a stronger part of the magnetic field, so you get more output and more low end. Moving it away gives you less output but more clarity and a cleaner attack.
The magnet pulls on the steel string. Set a pickup too close and that pull fights the string's own vibration. You get killed sustain, a strange warbling or beating on held notes, and pitch pulled slightly out of tune. It shows up worst on the low strings and on the neck pickup, because that is where the string swings widest.
If you have ever had a guitar where the low E goes wobbly and dies early and you could not work out why, this is very often the answer. It costs nothing to test. There is a full walkthrough in the setup guide.
Potting and squeal
Inside a pickup are thousands of turns of extremely fine wire. If those turns can move even slightly, they will vibrate in sympathy with loud sound, and the pickup starts behaving partly like a microphone. At high gain that becomes an uncontrollable squeal.
Potting means soaking the finished coil in wax so everything is locked solid. Almost all modern pickups are potted, which is why they behave at volume.
Some vintage style pickups are deliberately left unpotted for a bit of extra air and responsiveness, and their owners then find they squeal in front of a loud amp. That is the trade, and it is a known one rather than a fault.
So if a pickup screams at you at high gain, that is microphonics, not amp feedback, and it is fixable by potting.
The myths, straight
"Body wood changes what the pickup hears on a solidbody"
Look at the chain at the top of this page again. String moves, field changes, voltage is induced, signal goes to the amp. The body is not in that chain anywhere. The pickup is not listening to the room, so it is not listening to your mahogany either.
Wood absolutely changes weight, balance, stability, how the guitar takes a finish and how it feels to hold, and those are real reasons to care. It is on acoustics, where the body genuinely is the instrument, that species matters to the sound. There is more on this in the wood guide, and plenty of people will disagree with me. Build one and listen for yourself.
"Higher DC resistance means a better, hotter pickup"
Covered above. It means more wire. More wire usually also means darker and more compressed, which may or may not be what you wanted.
"High output pickups sound more aggressive"
What a high output pickup mostly does is hit the front of your amp harder, so the amp distorts earlier. The aggression you are hearing is the amp, not the pickup. A boost pedal in front of a lower output pickup gets you to a similar place while keeping the clarity and top end that the hot pickup traded away.
"Coil splitting gives you a real single coil"
It gives you one coil of a humbucker, which is not the same object as a purpose built single coil. It is typically shorter, wound to different specs, sitting over different magnets, and it loses the hum cancellation the moment you split it. It is a useful sound and worth having. It is just not a Stratocaster in a switch. Wiring for it is covered in the electronics guide.
"Covers kill your tone"
A nickel silver cover has a small, measurable effect, taking a little off the very top end. Small. The reason it gets exaggerated is that people swap covers and pickups at the same time and credit the cover. A brass cover has a bigger effect, which is why nickel silver is what gets used.
"I need new pickups"
Maybe. But before spending the money, set the pickup height properly, because that is free and it is the single most under used adjustment on an electric guitar. Then have an honest look at whether the thing you dislike is coming from the amp, which is usually a bigger part of your sound than the pickups are.
Pickups are worth changing when you genuinely want a different voice, not as a first attempt at fixing a sound you have not diagnosed.
If you want to go further
The winding process itself, coil counts, magnet handling and building a winder are covered in the pickup winding guide. How pickups interact with pots, capacitors, switching and the rest of the circuit is in the electronics and wiring guide.
And if you take one thing away from this page, take the mechanism at the top. Almost every pickup question people argue about answers itself once you know what the device is actually doing.