Instrument Cable and Sound

Cables, by themselves, don't have a specific sound but you can alter the sound of your guitar dramatically. To give you a better understanding, let me explain the basic function of pickups and cables:

1. A pickup is a cored inductor that converts the mechanical energy of the vibrating strings into an electrical signal. A pickup has inductance and resistance.
2. A cable is a tubular capacitor that transmits the signal from the pickup to the amplifier. A cable has resistance and capacitance.

In combination with a high impedance system, like a pickup, the resistance of the cable is too low to influence the signal; but in a low impedance system, like a speaker, the resistance of the cable is essential.

The sound of an electric guitar depends mostly on the frequency, the intensity and the bandwith of the resonance. The resonant frequency (Fr) is the result of the interaction between the Inductance (L) of the pickup and the Capacitance (C) of the cable.

With this simple equation, it's easy to calculate the Fr when the values of the L and C are known. However, to calculate the shifts, the bandwith and the intensity of the resonance, which depends on the Resistance (R) of the circuit, requires some extensive knowledge of electrodynamics, but you can hear the shifts by slowly turning down the volume control of your guitar.

There is neither good nor bad inductance or capacitance, and when it comes to sound, we all have different preferences-what Charly calls a fat, creamy blues sound, Johnny may call it a dull or muddy sound. Till the early '60's, most cables were between 8 and 10 feet long and had an average capacitance of some 300 pico farad. Combined with a Strat Pickup having an average inductance of 2.4 Henry, the resonance was around 6000 Hertz. Then came these spiral cords with a capacitance of 2.4 nano (2400 pico) farad shifting the resonance of a strat a little above 2000 Hertz.

You might ask, "How does the effect my sound?"

Due to the resistance of a pickup and the load resistance of the controls, we increase the bandwith of the resonance, causing an output boost in the vicinity if the resonance. If the resonance is above 5000 Hertz, it's barely noticeable and may increase the sparkling highs, especially with 500 kOhm controls. Shifting the resonance to lower frequencies results in increasing brightness and at about 3000 Hertz, you'll get that famous "ice pick" sound, especially with the bridge pickup. Below 2800 Hertz, the harshness slowly disappears and below 1000 Hertz, the sound gets muddy. Try it... turn your tone control to zero and with a .022 micro farad cap, the resonance will be at 700 Hertz, with a .05 micro farad cap, it's at 450 Hertz. Now replace the cap at the tone control with a 2.4 nano farad (.0024 micro farad) cap, turn the treble and volume of your amp above 8 and you might get a bit closer to some of Jimi Hendrix's sounds; but don't forget he also used some cable with a much higher capacitance. However, just recently I saw somebody offering a 12 foot cable with a very high capacitance for above $300 and promising the Jimi Hendrix sound. Capacitance is capacitance, and you can get the same effect with 2.4 nano farad cap for less than 50 cents.

The higher the inductance and the higher the capacitance, the lower the frequency of the resonance. This explains why the same pickup can produce a sweet tone, a bright, harsh tone or a compressed, muddy tone - it depends on the capacitance of the cable, the resistive load of the guitar's controls, and the inductance of the pickup. As a player, I've always preferred cable with a very low capacitance, because that allows me tailor my sound by adding capacitors, inductors, and resistors to the circuit. For that reason, I introduced my low-capacitance cable in 1978 (at that time, George L was the exclusive national distributor for my products). Today, there are quite a few usable, affordable cables available with a relatively low capacitance. It would be a great help to the consumer if all cable makers would publish the capacitance to allow players to select the right one for their needs.

On a final note, in pursuit of perfection we have to recognize that for all the equations of cable resistance, capacitance, and inductance of pickups, we cannot use any DC (direct current) measurements. Don't forget that the AC (alternating current) resistance of a wire can be as much as ten times higher than its DC resistance. DC -- which never occurs in the output of a guitar -- flows through the entire cross-section of the wire, and solid copper has the lowest DC resistance for any given diameter. However, a guitar's output is AC, which flows only very near the surface of the wire, a small fraction of the cross section know as the "skin depth" -- and some compound steel wires, such as the copper-plated steel used in my cables, have a much lower AC resistance than a solid copper wire of the same diameter.