@maruaudio/dsp/distortion/chebyshev shapes a signal with a first-kind Chebyshev polynomial Tₙ(x) over the fixed-4× oversampling stage of @maru/distortion-oversampled-waveshaper. The polynomial uses the recurrence
T₀ = 1, T₁ = x, Tₖ = 2x·Tₖ₋₁ − Tₖ₋₂, x clamped to ±1so a full-scale sine of the input maps to its n-th harmonic. Each input is interpolated to four points, each shaped and stored at f32, filtered by the shared 31-tap FIR and clamped to ±1.
Parameters
| Setter | Range the setter enforces | Default |
|---|---|---|
setChebyshevOrder | floor(order + 0.5), then 1 to 100 | 50 |
initChebyshevNode() takes no sample rate.
Lifecycle
initChebyshevNode allocates the 32-value history → setChebyshevOrder → chebyshevNodeTick → resetChebyshevNode, which zeroes the history and marks the state uninitialized. The recurrence runs a fixed 100-step loop whatever the order. Ticks allocate nothing and do no I/O.
When to use it
Generating a chosen harmonic from a sine, or adding harmonics to a synth voice. Order 1 is the identity before the FIR.
Limits
- Mono sample tick, wet only, with the FIR's 15 oversampled frames (3.75 samples) of delay.
- The FIR reduces products above the oversampled band but does not remove them; high orders still alias.
- The input is clamped to ±1 before shaping and the output to ±1 after.
- Order changes apply at once.