The Physics of Electric Guitar Pickups as RLC Filters
A passive guitar pickup is not a full-range flat acoustic microphone. It is a resonant second-order low-pass filter composed of thousands of turns of microscopic copper wire wound around magnetic pole pieces. The coil possesses large Inductance ((L)), internal DC resistance ((R)), and parasitic Capacitance ((C)) between adjacent wire turns.
The Resonant Peak ((f_{ ext{res}})) and the Sound of Electric Guitar
When combined with the guitar cable's capacitance, the pickup circuit creates an acoustic resonance spike ((f_{ ext{res}})) where the pickup actually boosts sound by +3 dB to +8 dB before aggressively rolling off high frequencies at 12 dB per octave:
This resonant peak is the single most defining factor of guitar tone:
- Stratocaster Single Coils ((L approx 2.2 ext{H})): Peak sits between 3.5 kHz and 4.5 kHz, creating the signature airy "glassy bell chime."
- Gibson PAF Humbuckers ((L approx 4.5 ext{H})): Peak drops to 2.5 kHz to 3.0 kHz, creating the warm, vocal, throat-singing mid boost of classic rock.
- High-Output Metal Pickups ((L approx 10 ext{H}-14 ext{H})): Peak drops down to 1.5 kHz to 2.0 kHz, producing thick chugging lower-mids with rolled-off treble.
Why 20 Feet of Coily Cable Destroys Pick Attack
Every standard guitar cable is a coaxial capacitor, adding roughly 30 to 50 picofarads (pF) per foot. A 20-foot vintage coiled cable adds over 800 pF of capacitance across your pickups. Because capacitance sits in the denominator under the square root, adding cable length physically drags the resonant peak downward into the murky midrange, killing harmonics and pick snap ("tone suck").