FilterBank4U
About the Project
FilterBank4U is an audio effect plugin that reimplements the filter and distortion signal path of the classic Tone2 FilterBank3. The original was only ever available for Mac as a 32-bit build, so this project provides a native 64-bit rebuild focused on the parts that really matter: two multi-mode filters plus tube and hard-clip distortion.
It ships as both a VST3 plug-in and an Audio Unit, so it works in any modern VST3 host as well as in Audio-Unit-aware applications like Logic Pro, GarageBand, and MainStage. The Audio Unit simply wraps the very same VST3 binary, so both formats behave identically.
Signal Chain
input ──► Filters ──► [Drive] ──► Distortion ──► [Dry/Wet] ──► [Volume] ──► [−8 dB] ──► output
The distortion sits after the filters in the signal path, matching the original. A fixed −8 dB output stage brings the nominal output level down by 8 dB.
Serial: input ──► Filter 1 ──► Filter 2
Parallel (default): input ─┬─► Filter 1 ─┐
└─► Filter 2 ─┴─► 0.5 · (F1 + F2)
The two filter slots can be wired in series or in parallel. In parallel mode (the default), the input feeds both filters and their outputs are averaged, keeping the level stable — great for layering, e.g. a low-pass with a band-pass.
Parameters
| Parameter | Description |
|---|---|
| Bypass | Global bypass (standard VST3 bypass flag) |
| Routing | How the two filters connect: Serial / Parallel (default: Parallel) |
| Filter 1 Type | Bypass / LP 30 dB / BP 15 dB / BP Moog |
| Filter 1 Cutoff | 20 Hz – 20 kHz (logarithmic) |
| Filter 1 Resonance | Filter Q (high values self-oscillate) |
| Filter 2 Type | Bypass / LP 30 dB / BP 15 dB / BP Moog |
| Filter 2 Cutoff | 20 Hz – 20 kHz (logarithmic) |
| Filter 2 Resonance | Filter Q |
| Distortion Type | Bypass / Tube Amp / Hard Clip |
| Drive | Amount of signal fed into the distortion |
| Dry/Wet | Blend between the raw input and the processed signal |
| Volume | Output level, −24 dB … +24 dB (center = 0 dB) |
Filter Types
A low-pass with a 30 dB/octave slope — a resonant biquad, a Butterworth biquad, and a single pole in cascade, with resonance driving the peak at the cutoff.
A band-pass with a 15 dB/octave slope — a resonant biquad band-pass whose resonance knob controls the bandwidth and peak.
A band-pass with a classic Moog diode-ladder response. A one-pole ladder with feedback through a diode soft-clip gives a fat, musical peak and gentle self-oscillation at high resonance.
Distortion
A smooth, bounded soft-clip with a touch of even-order warmth and drive-dependent gain — saturated, but never exploding in level.
An aggressive, symmetric flat-top clip, driven harder for a denser, harsher set of harmonics. The abrupt linear-to-flat transition is the signature hard knee.
Presets
The editor has a dedicated Presets section: save the full parameter set to a small, human-readable .fbkp file and load it back again at any time. The files are versioned and forward-compatible, so old presets keep working when the plugin gains new options.
Under the Hood
- Built on the Steinberg VST3 SDK and VSTGUI, compiled for Apple Silicon (arm64) & Intel (x86_64).
- The DSP engine is written in pure, VST-independent C++ and is fully unit tested (47 tests).
- Passes all 47 tests of the official Steinberg VST3 validator.
- Sample-accurate, glitch-free parameter automation and independent per-channel filter state.
- The oscillators, step sequencer, envelope, and delay from the original are intentionally left out.