Reference

Anti-Aliased Tube Lane

Look up syntax, contracts, layouts, algorithms, and exact behavior.

The tube lane is the main harmonic engine. It uses a smooth saturating transfer with small, controllable asymmetry so that low-order even and odd harmonics can be introduced without the abrupt spectral spread of hard clipping. In the implementation, the quality selector controls the number of internal ADAA evaluations used over the current sample segment.

Low-order harmonic emphasis. The intended tube contribution is weighted toward second and third harmonics, with higher partials declining quickly.

u[n] = g[n]x[n] + b[n]

Tube input. The tube shaper receives the pre-emphasized sample multiplied by dynamic drive and offset by a slowly moving bias.

The lane is normalized around a dynamic bias term. Bias subtraction removes most DC introduced by asymmetry, while the later DC filter and stereo-protect stages handle residual drift. Hearth keeps this lane deliberately low-order; the goal is thickness and curvature, not foldover effects.

y_T[n] = f_{\mathrm{ADAA}}(u[n]) - f_{\mathrm{ADAA}}(b[n])

Bias-compensated output. Subtracting the transfer evaluated at the bias point keeps asymmetry musically useful without allowing persistent DC to dominate.

Anti-Aliased Tube Lane

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