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Cable structure
A shield cable for electric guitars looks like the picture left.
The core(+, hot wire) is wrapped with insulation, shield(-, ground), and outer jacket in order.
As a guitar signal with high impedance of 20 ~ 40 KΩ is susceptible to noise and interference, shielding(-) must wrap around the signal(+, hot) wire.
Shielding for guitar cable is of braided or spiral shape. Factors like shielding material, shielding tightness, shield distance from hot wire, thickness of insulation, hot wire material, and number of strands all affect the guitar sound.
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Cable Capacitance
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The structure of cable is similar to that of capacitor in that they have insulation between + and - poles. So every cable has its own capacitance proprotional to its length as illustrate above.
As mentioned in Guitar Electronics, capacitor has a tendency to leak higher frequency range, resulting in a loss of treble in guitar signal. Especially in high impedance signal around 20 ~ 40 KΩ like in electric guitars, the signal will lose much more treble than in lower impedance signal.
Usually shield cables for guitars have capacitance of 30 ~ 50 pF(1 pico Farad = 10-12 F = 10-6 µF = 0.000001 µF) per feet(30 cm).
Assuming cable capacitance 40 pF/ft and a capacitor installed in tone control 0.022µF, 550 ft (168 m) shield cable will sound as dull as when you turn down the tone control to zero.
This kind of calculation may seem somewhat impractical, but strongly suggests that you have to take cable capacitance into consideration in sound making.
Considering treble loss by cable capacitance, approximately 18 ft (5.5 m) is the maximum length of cable for sound quality, which means you have to use just one cable directly from guitar to amp. If you are to put pedals in between or use longer cable, you need SOMETHING to compensate for loss of treble.
We will talk about this SOMETHING in Buffer (Line Driver).
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