Coaxial wire (and why it’s the best)
“Man, you really are such a nerd aren’t you?” Yes. Yes I am. And I actually enjoy talking about what kind of wire you use in your guitar. I do.
So this picture above is of coaxial wire (co=on the same, axial=line). It has two conductors (pieces of metal) in one wire, which is perfect for guitar work since there are only two “sections” of any given guitar circuit: signal and ground–unless it’s an active circuit, but that’s for another post. In passive guitar circuits, you’ll only ever have signal and ground, even with complicated switching and tone shaping. So this wire can connect both signal leads and grounds all in one elegant wire, but that’s not even the coolest part about it!
It also keeps all the signal runs shielded!
What’s shielding?
Well, you’re going to get me started on a long one, so buckle in.
So, electricity is just a bunch of atoms losing and gaining electrons, which are negatively charged ions. When electrons bond to protons–which are positively charged ions, and therefore attract electrons–a tiny electromagnetic field gets generated. If this happens fast enough, and with enough electrons, you can actually see the field getting generated along with a lot of heat, which eventually turns into light. That’s how lightbulbs work–at least in my highly simplified version of particle physics.
In an electric guitar, the signal generated by your pickups is also made up of moving electrons, and it has it’s own electrical field too! If it gets disturbed by other electromagnetic fields nearby, tiny voltages can get induced into the signal, (in kind of the same way that your pickups induce audio signal) which will manifest as noise. You definitely don’t want noise in your audio signal before it gets to your amp, because your amp makes everything you send to it a whole lot louder, noise included!
Things like fluorescent lights, computer screens, box fans, high wattage lights, WiFI routers, and all kinds of other electrical devices will generate fields that can interfere with your guitar signal.
Fortunately, there is a way to protect your vibrating electrons from outside influence, and this is what we call shielding.
Maybe you’ve heard of these so-called “crazy” people wearing tin foil on their heads to protect themselves from aliens or government mind reading. Well, what they are doing is not actually in direct conflict with reality. It’s called a Farraday cage. Tin foil, when connected to ground, will actually “shield” whatever it surrounds from electromagnetic fields, think radio frequencies, which are just really… really… ridiculously fast waves of sound. Tin foil isn’t the absolute best shielding material, so we don’t use it in guitar circuits, but copper does a great job of absorbing most frequencies over 100kHz. Carbon does a pretty good job too.
So, what is actually happening when we shield electrical devices? I’m glad you asked!
If you surround wire that carries audio signal that you want to protect with some kind of shielding material and connect that material to ground, the electromagnetic fields that would normally interfere with your signal will be absorbed by the shielding material, given a low resistance path to ground, and will go there instead of to your audio signal. Simple! And fascinating, I know!
In a guitar, you can use copper shielding tape to line the inside of your control cavity, or you can even use conductive carbon or silver shielding paint to essentially paint a Farraday cage around all of your guitar electronics. Or, you can use coaxial cable! This is one of the best ways to protect your guitar from making unwanted noise.
But it’s not a total solution! What about frequencies below 100kHz? Well, unfortunately there isn’t a simple solution to this problem for guitars yet. You would have to use a separate shield made of a complex alloy like mu-metal or permalloy. HIFI audio companies make cables with of both kinds of shields, but it’s considerably more difficult to put two kinds of conductive material on the inside of a rather large and oddly shaped guitar control cavity.
The main problem this leaves guitars with—as you may already be familiar—is commonly referred to as 60 cycle hum, or if you’re in Europe, 50 cycle. It’s also sometimes generally called “mains hum.” This is the magnetic field generated by the electricity in your walls. Your electric company provides you with access to all the electrons you want, but at specifically 120 or 240 Volts of pressure. This standardization of Voltage is what allows electronic device manufacturers to design the circuits in their products.
So the loads you put on your home supply of 120V, like your toaster, or your amp, will draw current depending on the voltage and the amount of resistance in the circuit—remember Ohm’s Law from elementary science class? Most devices will do this fancy trick called stepping down the voltage by using a transformer, which converts voltages through the process of inductance—yes, just like your pickups! Transformers are not just giant anthropomorphized robots, they’re in those “wall warts” that you use for your guitar pedals, stepping 120V down to the 9V that your pedals require, and they’re in your amp too, except most amps will step the voltage up, which is why they can be dangerous to work on.
But what does all this have to do with that infernal hum in your guitar? Well, that 120V supply is alternating current, which goes in and out, back and forth. And it does all this pushing and pulling at a specific speed. I’ll give you a guess what that speed is. That’s right! 60 cycles. What that means is that the hum will go in and out 60 times every second. 60 cycles per second, or 60 Hertz (Hz). That is the frequency with which it repeats. The movement of electrons in and out of the wires in your home generates a magnetic field which can interfere with other electrical circuits that aren’t shielded, like your guitar! Since you are amplifying the electrical signal generated by your guitar and converting it back into sound waves through the use of a speaker, that interference—at 60Hz—will also get amplified and converted into sound.
Unfortunately shielding can’t protect against 60Hz hum, but humbuckers can! But I’ll spare you today and save that for another post.
You might also notice that tiny, irritating buzz that goes away when you touch your strings or any other metal part of your guitar that’s grounded. Part of the reason we want to have our strings grounded is that they act as antennae and pick up some of the electromagnetic interference in the area around your guitar just like the coils of your pickups do. Because your strings also pass through the magnetic field generated by your pickups, the noise that they are picking up will get transferred to your signal if it doesn’t have a way to get to ground.
So if the strings are connected to ground, why is there still noise? And why does it get softer or silent when I touch metal stuff? Well, simply put, because you make noise too. You are a big electromagnetic fleshy transducer, and when you touch the strings, which are grounded, all that noise you are making gets sent to ground too! Unbelievable but true!
Coaxial wire will protect your precious guitar signal from interference better than most other shielding schemes, which is why I like it so much. It’s also the cleanest looking and easiest to work with. You can buy it in spools or in short lengths online. As you might have noticed in the first picture, the easiest way to use this stuff is to get a dental pick and pull the braided shield until it frays about a quarter inch or so back from the center wire. Yes, this technically decreases the shielding, but if the audio signal gets shorted to ground, you won’t have any signal to protectl! After loosening the braid with the dental pick, I twist it into a little tail, solder it right in the armpit, and clip it so it stays nice and tidy.
Once you have your wire all prepped, you can put it wherever you want! Connect all your chassis grounds with it and send it all to your output jack! The signal stays safely protected at the same time as the grounds are all connected, as they should be.
Phew. Well, I’m sorry if I lost some of you. I warned you that I like to talk about this stuff. I’m happy to elaborate if anything is unclear, and I welcome any corrections! I like to think I know it all, but I’m often humbled by those that know more, and wholly embrace the experience and the chance to improve.
Thanks again! See you next week!
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