Did you know that your guitar cable is a capacitor? Well it’s true. It’s a capacitor just like the tone knob on your guitar. Now capacitors have a dirty reputation since they create capacitance and that causes signal loss (which is bad). Yes, while we do use capacitors all the time for good things like equalization, there is a key difference: your guitar cable was never meant to be one.
So what exactly makes your guitar cable a capacitor? All you need really to make a capacitor is a pair of electrical conductors with an insulator between them. So does our guitar cable have the ingredients? Let’s see now shall we? Imagine that we could peel back the layers of a standard guitar cable like it were an onion. The outer level is the cable jacket. Maybe it’s tweed or plastic. But what we want to see is underneath the jacket. So let’s take off the rubber jacket. The next level is the metallic sheath. Most likely it is braided metal. Metal conducts electricity, right? So we have one conductor now, don’t we. Let’s keep going. Take off the metallic sheath. What is underneath? It’s a dielectric insulator. This is similar to the outer jacket. Since it is an insulator, it does not conduct electricity. It’s purpose is to protect the core. So we have one conductor and an insulator. Now we just need one more conductor to be in business. So let’s remove the insulator to see the final layer. This is the center core. It’s a metal conductor. Maybe it’s stranded copper. Bingo. You see we have the three ingredients to make a capacitor. So is this good or bad? Well, if a capacitor is good for nothing else, it is good for creating capacitance. But when it comes to our guitar signal, capacitance is very bad. I know, say it ain’t so, Joe…..
So why is it bad? We want the signal that reaches the guitar amplifier to be exactly the same as the signal that leaves the guitar. Now imagine there is a villain who stands in the way of your guitar signal reaching its destination unchanged. Well this villain is capacitance, and he is the bane of our guitar cable’s existence.
Now the reason unwanted capacitance is bad, is because a capacitor acts like a low‑pass filter. (This is an observed phenomenon of science and electricity just like making a capacitor.) That’s why we use them for our tone knobs. The way it works is fairly straight forward. A low-pass filter is a gate that won’t let through frequencies above the cut-off. The lower the cut-off level is, the more high frequencies there will be that will not be able to get through. That’s how you use it to roll off the treble on your guitar signal (by changing the cut-off level). Now let’s pretend our villain is a bouncer at a hip Hollywood dance club. Think of your signal as a group of friends hoping to have a fun night out on the town. Now let’s say this bouncer doesn’t like tall people. So he only let’s those of middle height and below into the dance hall. The tall people have to go elsewhere. These tall people represent the higher frequencies. The middle people are your mid’s, and the short one’s are your lows. Well is the group of friends in the club the same group that arrived at the door? There answer is no. This is also why long cables get such a bad rap. This is because another observable law of electricity is that the larger the surface area of the conductors, the larger the capacitance. More capacitance means more treble frequencies that can’t get through. Bye bye more of you tall fellows. Longer cables have a bigger tougher bouncer at their door.
What next? Is there not a hero among us? A body who can stand up to this villain. The answer is yes! In fact, there is not just one but several items of gear that you can use to battle capacitance. I will tell you of these brave heroes another day. But in the meantime, do not lose hope. The fight against this evil tyranny can be won!