How Electric Guitar Pickups Work
Have you ever wondered how a guitar pickup generates a signal for your electric guitar? That's what this video is about, and welcome to a brand new segment.
How Do Electric Guitar Pickups Actually Work? (Guitar Science)
This video is going to be kind of nerdy, all about the science of a pickup and why it works. I'm going to do my best to make this easy to understand, but this is a kind of complicated subject.
I'm not an electrical engineer. I'm just a guitar player who makes YouTube videos, which means I'm going to do my best. I've done a lot of research and all I ask in return is that you like this video and consider subscribing.
Motors
Before we start looking at pickups specifically. I think all of this is a little bit easier to understand if we start with electric motors. Electric motors are everywhere, from your ceiling fan to your garage door opener, you are interacting with them all the time.
Inside a motor, there are conductive coils and magnets. Electricity is supplied to the coils at specific intervals, which creates an electromagnetic field that pulls that coil toward the magnet.
The coils are attached to a shaft, so as they are pulled toward the magnet, the shaft turns.
We have a few key pieces here. There's a conductive coil, a magnet, electricity, and motion. In the case of a motor, you are applying electricity to create motion, or in other words,
Magnet + Coil + Electricity = Motion.
Generators
If we remove electricity but add motion to the equation, you're creating a generator. I have attached the two leads on the back of the motor in my pickup winder to my power indicator light. And as you can see (in the video), when I turn the motor by hand, the light flickers.
By applying that motion, it creates electricity. This is a variation on what I said before,
Magnet + Coil + Motion = Electricity.
And this is exactly how wind turbines, water turbines, or gas-powered generators generate electricity.
With an understanding of a motor and a generator. Now we can start looking at pickups.
Pickups
If you haven't seen my video where I build a single coil pickup, you should go check that out, because there's a little more information about pickups in there, but the basic components of a pickup are some copper coils and magnets. And since we're using a pickup to create an electrical signal, it's acting kind of like a generator, which means we need some motion.
Because there are magnets within pickups, there's already a magnetic field, so we just need something that can interact with that. Here (in the video), I'm going to connect this pickup to a multi meter. And because my screwdriver is made from magnetic material, it will interact with the magnetic field of the pickup.
If I wave the screwdriver close to the pickup, it should create an electrical current and you can see that on the multimeter.
So when you take that pickup and you put it in a guitar, the strings are made for magnetic material which means they will interact with the magnetic field of the pickup. And the signal that you're going to get is based on the wavelength and frequency of the strings that are vibrating.
Here's a formula that can be used to calculate frequency of a guitar string.
As you can see, it takes the string tension and thickness of the string into consideration, which explains why the low E string sounds different than the high E string.
If this is all starting to sound kind of confusing, don't worry, I'm going to break it down a little bit more. If you pluck an open string on your guitar, the wavelength is double the distance from the saddle to the nut, so it's double the length of the vibrating portion of the string.
If you pick that same string at the 12th fret, which is exactly halfway between the saddle and the nut, the wavelength is the distance from the saddle to the nut.
As the wavelength gets smaller, the frequency increases. So every time you fret a string, you're changing the wavelength, which is going to change the frequency.
If you bend a string, the pitch gets higher, but you're actually making the wavelength a little bit longer, but the frequency is higher because the tension on the string is increased.
So with just a couple variables, you can start to see how every single note you could play on the guitar would have different wavelengths and frequencies, which means a different signal would be generated through the pickup, which is why your guitar signal sounds like the note you're playing.
Harmonics
Another way to visualize wavelengths is through natural harmonics that you can play on the guitar. Common ones being the 12th fret, 7th fret, and 5th fret. I already said before that the 12th fret is exactly halfway between the saddle and the nut, so when you play a harmonic on the 12th fret, it makes the same note as if you fretted the 12th fret.
When you play a harmonic, you're basically just splitting up the wavelength. These natural harmonics can be played anywhere that the fretboard can be divided by a whole number. So at the 12th fret, you're splitting the fretboard in half. Seventh fret, you're splitting the fret board in thirds. Fifth fret, you're splitting the fretboard into fourths.
When you split the fretboard into fourths, you would have two full wavelengths across the length of the fretboard. This is also why if you play a harmonic on the fifth fret, you can lightly touch the string over the 12th fret without dampening the sound.
And that's because the 12th fret would be at the end of the wavelength.
My brain is starting to hurt, so that is going to be the end of this video. I hope all of that makes sense. If not, I'm sorry. If you want to know a little bit more about pickups, go watch the video where I build one.