Pickups and amps
How the electric guitar turns vibration into a signal, what changes between single coils and humbuckers, and what each amp stage does.
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Content under musical review. It may contain inaccuracies.
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How the electric guitar turns vibration into a signal, what changes between single coils and humbuckers, and what each amp stage does.
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An electric guitar barely makes a sound unplugged. Its voice starts in the pickups, which turn string vibration into an electrical signal, and is completed by the amp and the speaker. Every link in the chain shapes the tone.
A clean chord, where you can pick out every note:
With heavy saturation, full chords get muddy; that's why rock leans so much on the fifth chord:
Saturation clips the peaks of the wave. The more it clips, the more it looks like a square wave and the more new harmonics appear. Compare these two waveforms in the sound lab:
Unclipped wave Heavily clipped, nearly square waveOn your own electric guitar, play the same note with each pickup selected and with the guitar's volume knob at full, half and low. Listen:
Magnetic pickups. A magnet and a coil of very fine wire. The steel string vibrates inside the magnetic field and varies the flux through the coil, which induces a small voltage. That's why they work with steel strings and not nylon.
| Type | Build | Character |
|---|---|---|
| Single coil | one coil | bright, defined; picks up mains hum |
| Humbucker | two coils in opposition | hotter, warmer; cancels hum |
| Piezo | crystal under the saddle | common on acoustics; senses mechanical vibration |
Position matters too: near the bridge the string moves little and the pickup hears more high harmonics; near the neck it moves more and the fundamental dominates.
Amplifier. It has stages:
Amps can use valves (tubes), solid-state circuits or digital modelling. When a stage receives more signal than it can handle, it clips: that's saturation, the basis of overdriven and distorted tones.
Gain sets how hard the preamp is driven; master volume, how loud it is. Low gain with high volume gives you a loud clean sound. High gain with low volume, a quiet saturated one. Use your guitar's volume knob as one more pedal: from driven to nearly clean without touching the amp.
The two coils are wound in opposite directions and their magnets have opposite polarity. External hum induces opposite voltages in each coil and cancels out; the string's signal, which also depends on magnet polarity, adds up. Hunter also explains that the coil's inductance and the cable's capacitance form a filter with a resonance, giving each pickup its own presence peak.