How Pickups Work
OK! Here we go! Pickups are just magnets with a whole bunch of really thin, usually copper wire wrapped around them. You can call them “transducers” if you like, or “inductors,” or even “variable reluctance sensors” if you’re a nerd. The point is that the wire is insulated, unbroken, and has a beginning and an end, which we’ll call “positive” and “negative.” The magnets are polarized too—positive and negative—which we’ll want to keep separate in our minds. So, positive and negative pickup leads, and positive and negative magnetic polarity. Different things. Good. I guess you could call the magnet polarities north and south if that’s easier. This is all relevant (I promise) for figuring out the phase between two pickups, which we talked about over here.
I’ve borrowed the beautiful image above from Seymour Duncan because it’s the most perfect diagram of a pickup I’ve ever seen.
Pickups are often measured in terms of resistance. This is because there is so much wire going around the pickups that it actually does resist the flow of electricity. As you might imagine, the more wire that is wrapped around the magnets, the higher the resistance. There are different factors like the thickness of the wire and magnet strength that can also affect the total resistance, which is also why looking at resistance alone isn’t an exact way to determine what a pickup will sound like. Now that I’ve convinced you otherwise, it’s important to note that even though pickups do have resistance, they are not technically resistors, but inductors!
An inductor is just a whole bunch of wire wrapped in a coil. It’s different from a resistor because it doesn’t actually resist the flow of current, it just resists changes in current. This is because it takes so long–“hurry up grandma, I have to pee!”–for the electrons to get from one end of the coil to the other. It’s just like your trusty garden hose coiled up neatly near the spigot, or if you’re like me, sprawled all over the yard, drying to a crusty, disintegrating husk in the sun, and covered in dirt. When you turn the water on, it takes a little while to get to the end of the hose, and then if you turn the water off, the leftover water still flows for a little while! Hmm!
The inductance of a coil is measured in Henries (H), and some pickup manufacturers will have that value listed on pickup specifications. More inductance tends in practice to sound like more volume, thus more bass and low end frequencies and a “muddier” signal. An inductor doesn’t require a magnet, but using one increases the inductance a whole bunch! Adding a magnet to the coil also has the benefit of creating a larger magnetic field, which guitar pickups use to interact with the metal strings of your guitar.
In a pickup, type and strength of magnet will also affect the tone, as will the distance it is is from the strings, or even the distance of each individual magnet to each string, or—heck!—even the physical size of the magnet or the shape of the coil wrapped around it. There are as many varieties of tones to get out of guitar pickups as there are ways to construct them.
Now that I’ve complicated things sufficiently, I’m going to speak in broad, simple strokes. In general, the higher the resistance of the wire coil, the higher the volume of the pickup, and the darker the tone. This is why “hot” pickups and “high wind” pickups are marketed as being louder and great for metal and heavy shredding. It’s important to remember, though, that with that volume increase, you also usually sacrifice some clarity and definition in the high frequency range. This is the main difference between “modern,” “hot” pickups and “vintage” pickups, which tend to have more clarity and note definition, if a little lower output.
Now that I’ve got you to thinking of pickups inductors, here comes another wrench: it’s really (really) best to think of pickups as transducers, which is a word that we use to describe any device that converts energy from one form to another—like converting the vibrational energy from your strings into electrical signal! The way it works is that the vibration of the steel core of a guitar string disturbs the pickup’s magnetic field, which then pushes and pulls the electrons in the coil of copper pickup wire at the exact frequency of the vibration of the strings, “converting” it into a tiny electrical signal that goes through your guitar electronics, then through your sick pedal rig, and an amplifier that sends it to various gain stages, effectively making it a whole lot louder. Cool, right?
So to make use of these electrons in the pickup wire getting pushed and pulled around by those vibrating guitar strings, they need a place to go. Since the way we control electricity is by putting it into a “circuit,” we need the negative lead connected to ground, and the positive lead connected to the rest of the circuit. So the positive lead of a pickup will be the beginning of our “signal path.”
It’s as simple as that!
But what about these “variable reluctance sensors” you mentioned?! Back in the closet, nerd!
See you next week!