Simulation mode

Measurement, run backwards. Every other view answers “here is a circuit — what is its fingerprint?” Simulation mode answers the inverse: “here is a fingerprint property — what does it sound like, and what do the charts do when I change it?” You get a virtual pedal whose knobs are the fingerprint dimensions, and every chart follows the sliders live.

What it is (and honestly is not)

The virtual pedal is a small software circuit: a filter, a clipper, and a filter, with knobs for the properties the rest of the app measures. The charts you see are not drawn from formulas — PedalScope runs its real measurement pipeline against the software pedal, the same sweeps and two-tone tests it plays through your interface, just with no cables. While you drag a slider the app uses shorter “interactive quality” sweeps (labeled at the top); the Full Quality button re-runs the standard configuration. The chart strip carries every measurement kind in the same order as the rest of the app, the waveform matrix included: while you drag it is a 3×3 grid (the reference lattice, nested in the standard one), and Full Quality measures the standard 5×5. Nothing here processes your instrument live, and no preset is a model of a product — each is named for what its clipper does.

That dogfooding is the point: if simulation’s charts and measurement’s charts ever disagreed, one of them would be lying. Because they share one pipeline, the virtual pedal doubles as a standing test of the whole measurement stack.

One difference is built in, and it is stated rather than hidden. The virtual pedal applies its clipping shape to the signal sample by sample at the session’s sample rate, so the harmonics it makes near the top of the band fold back across it — an aliasing error that a real pedal measured through a real interface does not carry, because the interface’s converter removes that content before it is sampled. The error is largest for hard clipping and for the highest harmonics: measured against the exact answer, the top orders read a few decibels off in their highest half-octave, and a hard clipper’s even orders, which its symmetry should leave absent, read as a faint floor under the fundamental. Reads well inside the band are the virtual pedal; reads in each harmonic’s top half-octave carry the simulation’s own limit, which the measurement pipeline reading them does not add.

The knobs, and the chart each one drives

Drive and the clip threshold are deliberately in different units: drive is a gain before the clipper, the threshold is where its knee sits. The line under the Clipper group relates them — how far the signal lands above or below the knee at the standard measurement drive (−26 dBFS, which reaches the virtual pedal as 50 mV pk since its volts are full-scale volts; on a calibrated rig that same drive is PSC-1’s 168 mV pk anchor), so “+20 dB” and “±0.60 V” read as one fact: 1.6 dB under the knee.

The flagship experiment: set asymmetry to zero and look at the Harmonic Distortion chart — the even-order stems sit at the floor, because a perfectly symmetric clipper cannot create them. Now drag the slider and watch H2 rise out of the noise, then press play on the Symmetry morph panel below the transfer curve and hear what you just measured.

▶ Open the asymmetric Fuzz preset

Presets

Five starting points. Four are named for the flavor they chase, not the circuits they’d need to be: Hard clip (Si) and Hard clip (LED) differ only in clip threshold — measure both compressions and the knee moves by the diode ratio, about 9 dB. Soft overdrive is a soft knee behind a bass-cutting pre-filter. Fuzz is asymmetric with almost no headroom. (Builds before 2026-09-05 gave these other names; the links below still open them, and a snapshot saved under an old name keeps it.)

The fifth is the odd one out, and it is worth your time first.

Linear (no clipping) — the null case

Linear (no clipping) is a virtual pedal that does nothing. Its drive is unity and its clipper’s corner sits more than 13 dB above anything the app can send at it, so the clipper is the identity function for every signal it will ever see — linear by construction, not by being quiet. All that is left is the pedal’s filter pair, parked at the ends of their ranges.

Measure it and read what the charts say, because this is the one preset that tells you what the instrument does when there is nothing to find:

• The Harmonic Distortion chart shows a fundamental and nothing else. Not small stems — no stems: every order sits at the analyzer’s own separation limit, which is as close to “absent” as a synchronized sweep can measure.

• The compression view reports no knee at all — not a knee at the edge of the probe, and not a guessed one. A hinge fit will always find a breakpoint if you let it; this one declines, because a straight line has no bend to locate.

• Its cleanup reading says the device is clean across the whole probed range instead of quoting a level. That is the three-state reading doing its job: “clean everywhere” and “cleans up at −40 dBFS” are different facts and never share a sentence.

• The transfer curve draws a straight line, and the waveform pane beside it declines to draw a shape at all. With no harmonic content to carry, any wiggle it drew would be the machinery’s own arithmetic rather than the device — so it says so instead.

Filters are not distortion, and this preset is where that becomes concrete — its post-filter shapes H₁ across the chart while every higher order stays at the floor. A tone control changes what you hear; it does not add harmonics.

▶ Open the Linear preset — measure nothing, on purpose

▶ Try Hard clip (Si)

▶ Try Hard clip (LED) — then compare the knees

Matching a real pedal

The Compare to Library section overlays a hardware Harmonic Distortion measurement from your library on the virtual pedal’s, with the same distance number the Compare view uses. Dialing the virtual pedal until the distance shrinks is the best exercise in the app: every move that helps teaches you which knob owns which part of the chart. Check the drive chips first — if the sweep levels differ, part of the gap is drive, not circuit character.

A snapshot of the virtual pedal can be saved to the library. It arrives marked simulated, with the full parameter recipe stored on the record — a measurement of software is still a measurement, but it never masquerades as hardware.

Common misreadings

• “The charts look coarser while I drag.” Interactive quality trades sweep length for responsiveness and says so in the header chip. Numbers you plan to quote deserve a Full Quality pass.

• The slew knob is not a tone control. A low-pass filter removes treble from the output; the slew limit distorts fast signals — quiet, slow playing stays clean while high notes and hard attacks grow extra harmonics. That frequency tilt in THD is its signature.

• Matching a fingerprint is not cloning a pedal. The virtual pedal has no supply sag, no temperature drift, no interaction with your guitar’s pickups. A close overlay means the static recipe matches at that drive — feel is a bigger word than that.

Try it now: open Simulation mode.