Circuit bench

A pedal circuit solved part by part, the way a SPICE simulator does it, while you listen and watch. Turn the knobs, change any part, or tap a wire to put a probe on it.

Room 25 °C

Note

Add

Pickup level

Peak voltage from the pickup for each note. A single coil strummed hard makes a few hundred millivolts.

Tap a part to change it. Tap a wire to probe it. Rust numbers are the DC voltages at each node. Scroll sideways to see the whole circuit.

Input

pickup, unloadedat the pedal input

Output

at the amp input

Probe

Spectrum

Match loudness

Output

Bias

What this means at the pedal.

How it works. Every part becomes an equation, and the circuit is solved many times per sample, 192,000 times a second while you drag and 384,000 once you let go, so the distortion doesn't fold its own harmonics back into the audio. Transistors use the Ebers-Moll model with gain, leakage, Early effect, base resistance, junction capacitance, and temperature. Their charge storage is set from the bias point, which is close for small signals and approximate while they switch hard. The transistor presets are representative values, not measurements of particular parts. Capacitors are ideal, and the battery is a voltage behind a resistance.

Part of the reference section at swellamps.com.