Frieve Vinyl Explained: A Physics-Accurate Stylus/Groove Simulator

Frieve's "Vinyl Explained" is not a toy — it's a browser-based, physics-accurate simulation of a stylus tracing a vinyl groove, built for engineers who want to understand what actually happens at the contact patch. The simulator uses Hertz/Winkler contact mechanics, viscoelastic damping, and rigid-body dynamics, all in SI units, and validates its output against real-world orders of magnitude.

What It Simulates

The signal chain starts with pink noise (or a sine wave) that passes through RIAA pre-emphasis, bass mono filtering, HF cutoff, and velocity-to-displacement integration. The result drives 45/45 left and right wall normal displacement. The 0dB reference is a 5cm/s peak wall velocity — a real-world mastering standard.

At the stylus tip, the simulation models contact pressure (~0.4GPa at 2g VTF), which exceeds PVC yield stress, meaning microscopic asperities in the ~5×7µm contact patch are crushed and averaged. Roughness is modeled as a three-scale AR(1) process, with analytic patch-averaging to separate visible roughness from what the stylus actually feels.

Tracing Distortion and the Bit Ruler

Distortion emerges from geometry, not a formula. The simulator evaluates the stylus scanning-radius parabola against the wall gap at each step, so inner-groove treble loss and pinch-effect distortion are direct consequences of the model. A built-in "Bit Ruler" divides a ±15µm wall displacement full scale along each modulation axis, showing the effective bit depth — at default settings, about 9.7 bits (DR 72dB).

Noise Sources

Groove roughness is the dominant noise source, calibrated to SNR 60dB. Dust follows a physical deposition model with flakes, fibers, and grit — only particles actually pressed by the stylus deform. Static is injected as an electrical pulse, not a mechanical vibration, matching real playback chain behavior.

Validated Orders of Magnitude

The simulator checks out against real-world measurements: 1kHz sine at 5cm/s yields output error <0.03dB and THD≈0.6%. Contact resonance is ~40kHz, cantilever static deflection ~0.3mm, arm resonance ~12Hz. These are not random numbers — they match actual vinyl playback physics.

What's Missing

The model simplifies to two degrees of freedom in the groove cross-section, omits groove-direction vibration and stick-slip, and doesn't handle wow, flutter, eccentricity, warp, or cartridge electrical loading. But for a browser-based tool, this is remarkably deep.