The body of an electric guitar is most often made from a solid block of wood. You pluck, strum, or pick the strings, and somehow this becomes an electrical signal that goes to your amplifier, which spits out something astoundingly louder than the sound of an unplugged electric guitar.
Even with a hollow or semi-hollow body electric guitar, you can be sure that the bulk of your volume isn’t coming from resonance within the guitar.
If you’re a detail-oriented person, or a science nerd like yours truly, demystifying what’s going on with the electronics of your guitar might be a useful and manageable first step on your path to tone mastery. You can get really deep into this stuff (and there are links at the bottom of this entry to help you start exploring if you like), but we’ll try to keep it practical here.
When you strum your guitar, each string vibrates at the frequency you’ve tuned it to, creating a repeating disturbance of the space around the string that continues as long as the string keeps vibrating. You probably know this – great! All the while, you’ve got one or a couple of magnetic pickups in your guitar. This is where the science happens: the construction of your pickups what allows mechanical string vibrations to be converted into an electrical signal that can be processed by the rest of the electronics in your guitar, pedals and amplifier.
The pickups in your guitar consist of a permanent magnet (a material that has been conditioned to produce its own persistent magnetic field) wrapped with a coil of thousands of turns of copper wire. Copper is a conductor, meaning that electric current may flow through it relatively uninhibited.
A magnetic field is a complicated concept. For now, it’s enough to know that it refers to the force that affects the space and electricity around and within a magnet in a consistent fashion. Because of this, the repeating vibrations of your guitar strings disturb the field, which in turn generates a voltage in the copper wire. Voltage is a difference in electrical energy between two points. This is what allows an electric current to move through your wire, since current tends to move from a point of higher energy to one of lower energy.
The fact that someone thought of this, and that it works, is pretty wild. You definitely don’t need to understand the physics behind magnetic fields to enjoy and excel at playing guitar, but it’s sure cool to think about, and the hope here is that the more you know about your instrument, the more comfortable you’ll be with it—especially when your electronics are giving you trouble.
So you’ve got a current going, now what?
Now that we’re in the realm of electric current, everything moves through wires. The current generated by your strumming is the signal you want to hear coming through your speakers. Essentially, it will make its way first to your volume potentiometer (or volume “pot”) and then to your output jack.
The volume pot works by allowing you to dictate how much of your current you want to allow to bleed to ground. “Ground” refers to a common metal point to which all of the electronics in your guitar are connected, such as the control plate or tail piece. One of the functions of grounding is to absorb any undesirable/stray frequencies your pickups are sensitive to that you don’t want to make it to your output jack or amplifier.
Turning up means less current escapes to the ground and more current goes on to your output jack; turning down lets more current escape.
As you know, when you plug a cable into your output jack, your signal can flow to the other end of that cable, which plugs into your amp.
The lug labeled “tip/signal” is where your guitar signal enters the jack. It is continuous with the actual “tip” of the jack. When you plug in a cable, a connection is made with the tip and the current (your guitar signal) flows into the cable and on to the amp.
You may have heard someone say of a buzzy guitar that it “probably has a grounding problem.” This means that some of those buzzy frequencies aren’t bleeding off to ground like they should be, and instead are traveling along your signal wires with the frequencies you want to hear. Much of the time this is because of one bad connection in your guitar’s wiring, which is a quick and easy fix if you know how to solder – a very learnable skill! The same is often true of a connection on your output jack if your signal is cutting in and out and you’ve ruled out amp problems.
Meanwhile, if you’ve got a “scratchy pot” (scratching sounds come through your amp when you turn the knob) your problem is often just dirt. You can definitely fix this yourself using a can of contact cleaner with a straw attachment:
- First, unscrew your control plate and lift if up.
- Pull the knob off the scratchy pot – you can really just lift it straight off – and look at the pot. There should be a little hole in the back of it.
- Spray some cleaner into this and turn the pot back and forth a few times to work it in. This should do the trick!
Below is a diagram showing one way in which all the parts we’ve discussed can be connected. You should be able to follow both the ground wire and the path your signal would take in a continuous path through pickups, volume pot and output jack.
Wires are soldered to the back of the volume pot for grounding
Note that this diagram does not include a tone knob or pickup selectors. Briefly:
- Pickup selectors are the switches on your guitar that control which pickups are “on.” When the switch for a pickup is engaged, a connection is made that allows the current to flow from that pickup to the volume pot and output jack.
- A tone knob is another kind of potentiometer (“knob” and “pot” are pretty much interchangeable here) that’s conditioned to only resist high/treble frequencies. When your tone knob is all the way up, none of the highs are removed from your signal. As you dial it down, you are “rolling off” more and more of your treble, allowing more of your high frequencies to bleed off to ground instead of flowing through to your amp.
This is a lot of technical information, but the point is this: an electric guitar converts mechanical string vibrations to electric current or “signal.” This happens by way of magnetic pickups, from which point your signal flows through a series of relatively simple electronics in the guitar, onto an instrument cable, and into your amplifier. An amp does a lot of things, but mainly it takes a what is still a very weak signal leaving your guitar and turns it into one that’s strong to be audible (depending on your amp, of course, “audible” may be a huge understatement).
Not magic, just physics.
Want to learn more about the science behind all this? Khan Academy offers some great tutorials, linked below!
More on pickups:
Pickups 101 from Seymour Duncan