VINAIultrabass — Manual

01Overview

VINAIultrabass is an intelligent tonal enhancer for the low end. At its core, a precision peaking-EQ bell points exactly where your sub lives — anywhere from 14.6 Hz to 240 Hz — and lifts it with transparent resonant gain. Running alongside is a parallel odd-harmonic soft-clip path that generates the upper harmonics (H3 / H5 / H7) the ear uses to reconstruct a missing fundamental, so the bass is felt even on speakers that can't reproduce it.

Both stages are driven by the Adaptive Harmonic Core. A lab-grade analyzer draws the blue bell response over real dB and Hz rulers with musical-note markers, pins each generated harmonic at its true frequency and tags the peak with its exact Hz, note and gain — while the Saturation Core panel shows the clipper's live transfer curve, per-harmonic ladder and THD. FREQ SNAP quantizes the boost to the nearest musical note so your low end locks to the key of the track.

02The interface

• Lab-grade analyzer (left) — the blue bell response drawn over real dB and Hz rulers with musical-note markers; every generated harmonic (H3 / H5 / H7…) is pinned at its true frequency, and a peak tag reads the exact Hz · note · dB of the boost.
• Saturation Core panel (right) — the clipper's live transfer curve at the current drive, a per-harmonic ladder (H3–H11, in dBc) and DRIVE / THD readouts.
• Frequency readout — the targeted frequency in Hz and the nearest musical note, with FREQ SNAP to lock to that note.
• Bell controls — FREQUENCY, WIDTH and BOOST shape the resonant low-end lift; BOOST reads in dB, the actual bell peak gain.
• Drive controls — DRIVE and DRIVE VOL push and blend the parallel odd-harmonic path.
• Output row — OUT, MIX, plus INIT and BYPASS.

03Knobs & buttons

Bell & saturation

Output & utility

04The Adaptive Harmonic Core

The engine runs two stages in parallel rather than in series, so each does one job cleanly. The bell adds resonant weight exactly where you point it; the odd-harmonic path rebuilds the translation harmonics on top. Because they're independent, you can run either alone or blend the two:

• Clean boost — bell only. Transparent resonant weight from 14.6–240 Hz with no added harmonics, for pure surgical low end.
• Harmonic drive — push DRIVE and raise DRIVE VOL so odd harmonics bloom on top of the sub and the bass cuts through on small speakers.
• Note lock — FREQ SNAP quantizes the bell to the nearest musical note, locking the boost to the key of the song.

The analyzer draws the bell response and pins the generated harmonics as you work, the Saturation Core panel tracks the clipper's transfer curve and THD in real time, and per-sample gain smoothing keeps every move zipper-free no matter how fast you ride the controls.

05Under the hood

Two paths run in parallel and sum at the output: a clean resonant boost and a harmonic generator. Neither is in series, so the bell never feeds the clipper and the clipper never colours the clean lift — each carries exactly one job.

Signal flow

Input splits into a boost path and a harmonic path. The boost path is a single peaking-EQ biquad. The harmonic path takes a band-passed copy, drives it through an odd-symmetric soft-clipper, and is scaled by DRIVE VOL. The two are summed, trimmed by OUT, then blended against the unprocessed dry signal by MIX.

• Boost biquad — a double-precision RBJ peaking-EQ section in transposed direct-form II. Double precision keeps the coefficients well-conditioned at sub-bass centre frequencies where single-precision biquads drift and lose denominator resolution.
• Harmonic path — a parallel band-pass feeds an odd-symmetric algebraic soft-clip, x / (1+|x|n)1/n. The odd symmetry means it generates only odd harmonics (H3 / H5 / H7…) — the partials the ear uses to reconstruct a missing fundamental — with no even-order content or DC offset. The clipped path is blended back in at the output.
• Parameter mapping — FREQUENCY, WIDTH (Q) and BOOST (gain) are not raw knob curves: they're driven from measurement-fitted mappings — a 21-point Hz table for frequency, a quadratic curve for Q, and an empirical gain surface — so the on-screen number and the actual bell response agree across the whole 14.6–240 Hz range.
• Smoothing — every gain (boost, drive, DRIVE VOL, OUT, MIX) is smoothed per sample with roughly a 4 ms time constant, so fast control moves and automation never produce zipper noise or coefficient discontinuities.
• Dry path — at MIX = 0% the wet sum is fully muted and the dry signal passes bit-exact; no biquad state, summing, or trim touches the samples on the dry leg.
• Latency — the chain is entirely biquad + memoryless waveshaping, with no oversampling, FFT or lookahead, so it reports and adds zero latency. No delay compensation is required from the host.
• Metering — the display is decoupled from the audio thread: the analyzer curve is computed from the current biquad coefficients, and the harmonic pins, transfer curve, ladder and THD readout are derived from the same drive mapping the engine runs on, so the GUI reflects the running DSP state without touching the processing path.

06Measured

Measured in-house (headless host + numpy/scipy), 48 kHz.

07Specifications