That magical instrument, the electric guitar



The induced electromotive force in any closed circuit is equal to the time rate of change of the magnetic flux through the circuit. Faraday's law of induction:

When I was younger I asked my mother if I could get a guitar and take lessons. Before giving me a firm answer she did some research and talked to a few people about it. Unfortunately, one of the people she talked to was a guitarist, who advised her that an acoustic guitar was better to learn on because there was no distortion of the sound and I wouldn’t need an amplifier. What she didn’t understand was that I didn’t want to play the guitar, I wanted to play the electric guitar.

I loved music but I wasn’t really a musician at heart. My passion was electricity and everything about it. My toys were electric motors, light bulbs, batteries and transformers. Making music with electricity was just an exciting extension of that. Well, a few decades later I still don’t have an electric guitar – yet, but I’ve been starting to think about it again.

An electric guitarist makes music with two powerful, but mysterious forces: The creative force and the electromagnetic force. There are other pickup technologies now but I’m staying with the original electromagnetic type for this article. It’s still the most widely used, and there’s a fascinating history to its operation that began in 1831.

Michael Faraday was a scientist captivated by invisible forces. He discovered that moving a magnet near a coil of wire induced a flow of electrical current through the coil. This behavior is at the heart of the magnetic guitar pickup. A row of magnetic rods (or screws) line up with each of the steel guitar strings. Surrounding these rods is a coil of wire. A single coil may surround the whole group or a coil may surround each rod individually. The image at right depicts the typical lines of magnetic field that would be present around each rod. The steel, or ferrous, guitar string would be tightly suspended above the rod, and its back and forth vibration disrupts these magnetic field lines just enough to move them relative to the surrounding coil. This produces the same effect that Michael Faraday observed in 1831, and essentially makes the guitar pickup an alternating current generator – somewhere in the very low millivolt range.

This technology is always where my fascination was focused when I looked at an electric guitar, but it always seemed somewhat mysterious. When you reveal the operation, however, you realize that it isn’t that complicated, and is well within the realm of the hobbyist to make.

Here is a video showing the complete workbench manufacture of a guitar pickup. There are quite a few videos like this online but I found this one to give the best visual instruction. I’m also including some resource links for parts and how-to advice. Maybe I’ll even build that guitar I always wanted…

Parts suppliers to make your own pickup:

Amplified Parts

Guitar Parts USA

An excellent in-depth description of pickup circuitry, operation, and performance analyzing

A Listing of electric guitar building tutorials