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ACOUSTIC REFERENCE & SYNTH · 2U Rack Extension · $9.00 USD (Intro Special) · v1.0.1

Kalibrus

Precision Monitor & Mix Reference, Expressive Noise Synth & Random Voltage Generator

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Tune Your Room, Balance Your Mix, Play the Noise

Kalibrus combines three essential studio tools in a single 2U rack extension: a precision acoustic monitor and mix reference, an expressive note-tracked noise synthesizer, and a generative random voltage source.

While engineered to laboratory acoustic tolerances, Kalibrus is built first and foremost for day-to-day music production, mixing, and sound design in Reason.

In the Mix: Five Everyday Production Workflows

1. Playable Synth Voice

Most noise generators just sit there and hiss. Kalibrus tracks your MIDI keyboard pitch with 1V/oct bandpass filtering. Play a C3, and the noise tunes directly to C3. Push your Mod Wheel, and the passband narrows down to a focused resonant bite—with automatic gain compensation to keep volume steady. With front-panel continuous generation disengaged, it gates and responds dynamically to note velocity, making it ideal for flute chiffs, wind leads, risers, or layering acoustic air over synth leads.

2. The Auto-Muting Tape Bed

If your tracks feel sterile or empty between notes, load up the “Tape-Band Noise Floor (-42dB)” patch and engage the AUTO button. With its built-in audio passthrough, you can drop Kalibrus straight across your mix bus without extra mixers or splitters. It injects a warm analog noise bed while your DAW plays, and silences itself automatically when playback stops so you never get idle hiss.

3. Beefing Up Drums & Claps

When a snare or clap lacks bite, trigger Kalibrus on hits (via MIDI or rear Gate In) to layer a burst of filtered white or pink noise underneath. Its Stereo Width dial (0% to 200%) lets you spread that top-end sizzle wide across the stereo field while keeping the core drum punch focused in the center.

4. 5-Minute Pink Noise Mix Balancing

The classic mix engineering reference shortcut, built right into the rack. Set pink noise to your target monitoring level (using the factory preset calibrated to -18 dBFS True RMS), solo each track or bus on your mixer, and bring the fader up until it just peeks above the noise floor. Go track by track, turn the noise off, and your overall balance is 90% dialed in without ear fatigue.

5. Generative Random Voltage (Sample & Hold)

Flip the rack around and patch the Gate-Triggered S&H CV Out into the filter cutoff, pan, or pitch CV input of another synth. Every time you play a note, Kalibrus fires a new stepped random voltage. Back off the destination synth’s CV trim knob for subtle analog drift that keeps repetitive loops organic, or crank it for generative sequencing.

The Three Noise Spectra

Kalibrus generates three mathematically pure noise colors, each tailored for specific acoustic and sound-design tasks:

White Noise (Flat Power Density)

Uniform energy across all audible frequencies. Essential for testing microphone responses, converter frequency linearity, comb-filtering diagnostics, and synthesizing snappy percussion transients.

Pink Noise (-3 dB/octave)

Synthesized using an optimized 6-pole (+1 FIR) Kellet IIR filter maintaining tight ±0.5 dB linearity across the full 20 Hz – 20 kHz spectrum. Calibrated to a bit-exact -18.00 dBFS True RMS reference at unity gain for instantaneous K-System monitor alignment and frequency-masking mix balancing.

Brown Noise (-6 dB/octave)

Synthesized via a leaky integrator with high-pass DC bias blocking. Delivers deep, organic low-frequency acoustic energy ideal for subwoofer tuning, room boundary resonance testing, and beefing up 808 sub-bass lines.

Tactile Control: Front Panel & Folded Strip

The interface provides immediate tactile control across both full 2U and compact 1U folded views:

Full 2U Rack Panel

  • Bay 1 (Power & Transport Sync): AUTO transport sync button (syncs noise to DAW playback), MAN manual override button (continuous noise for room tuning), and a NOTE indicator that lights during active keyboard or sequencer triggering.
  • Bay 2 (Noise Color & Spectral Sculpting): 3-way selector for active noise color (BROWN, PINK, WHITE), flanked by 4th-order High-Pass and Low-Pass cutoff dials (20 Hz – 20 kHz) for rapid frequency carving.
  • Bay 3 (Spatial Processing): 3-position stereo mode selector ([DUAL | STR | MONO]), continuous WIDTH dial (0% to 200% with constant-power normalization), and a center-detented BALANCE control.
  • Bay 4 (Noise Level & Metering): NOISE LEVEL dial with a 0 dB center detent, and dual vertical 20-segment calibrated RMS/Peak telemetry ladders (-48 dBFS to 0 dBFS) with peak-hold.

Built-In Audio Passthrough & Linear Summing

Rear stereo inputs labeled Inputs (Thru Raw) allow Kalibrus to sit directly on a mix bus or mastering chain without auxiliary mixers or splitters. When Kalibrus is idle, incoming audio passes through with bit-identical fidelity. When noise is engaged, incoming audio is cleanly summed at unity gain with zero gain offsets.

Compact 1U Folded Strip

When rack space in dense projects is at a premium, Kalibrus collapses into a compact 1U hardware strip with full access to its core controls:

  • Bay 1: AUTO and MAN engage buttons, NOTE activity indicator, and patch browsing controls.
  • Bay 2: Direct noise color buttons ([BRN | PNK | WHT]) alongside HIGH-PASS and LOW-PASS cutoff dials.
  • Bay 3: Stereo routing buttons ([MONO | STR | DUAL]), WIDTH, and BALANCE dials.
  • Bay 4: NOISE LEVEL dial and calibrated horizontal stereo RMS/Peak meters.

Expressive Synthesis & Keyboard Tracking

Kalibrus tracks keyboard pitch and MIDI dynamics for expressive performance:

  • 1V/Oct Keyboard Pitch Tracking: Connect MIDI keyboards or sequencer gates to pitch-track Kalibrus’s filter passband across the musical scale with last-note priority and pitch bend support.
  • Mod Wheel & Expression Bandwidth Control: Mod Wheel (CC 1), Expression Pedal (CC 11), and rear Bandwidth CV smoothly narrow the filter passband around the tracked pitch down to a focused 2-semitone resonant bite, with automatic gain compensation to maintain perceived volume.
  • Dynamic Velocity Sensitivity: Triggered notes respond dynamically to MIDI velocity and Gate CV amplitude, shaping transient burst attacks for drum layers and rhythmic accents.
  • Sustain Pedal Support (CC 64): Holding the sustain pedal latches the sounding noise voice and filter passband through note-off events, allowing hands-free performance while adjusting front-panel filter and spatial controls.
  • Click-Free Release: Filter cutoffs and sounded pitches remain solidly latched through a smooth 5 ms release fade, eliminating transient clicks upon note-off.

35 Production-Ready Presets

Kalibrus ships with 35 factory presets: 8 instant root Quick Starters for 1-click calibration, plus 27 specialized presets across 5 functional categories:

  1. Root Quick Presets (8 Presets): Instant starter and reference configurations including Quick - Pink -18 dBFS, Quick - White Flat, Quick - Brown Sub, Quick - AES-SMPTE, Quick - Speech Ref, Quick - Sub Probe, Quick - Vinyl Bed, and Quick - Dual Mono.
  2. 01 Reference & Calibration (10 Presets): Bob Katz K-System RMS monitoring references (K-20, K-14, Pink Stereo -12dB, True RMS Pink Reference -18dBFS), official AES/SMPTE Band-Limited Pink Noise (500 Hz – 2 kHz), EBU R128 (-23 dB CAL), Brown Noise Sub Reference, and phase coherence test checks.
  3. 02 Mixing & Diagnostics (5 Presets): Surgical frequency-masking diagnostic tools and auditory palate cleansers including Pink Noise Mix Balancing (-18 dB CAL), Lower-Mid Palate Cleanser (200 Hz – 500 Hz), Mid-Band Speech Reference, Upper-Mid Ear Reset, and Top-End Air Reset.
  4. 03 Acoustic Probes (4 Presets): Low-frequency room mode and boundary diagnostic tools for Subwoofer Tuning (20 Hz – 120 Hz), Sub-Bass Room Mode Probe (40 Hz – 100 Hz), Subwoofer Crossover Alignment, and Fletcher-Munson ear fatigue analysis.
  5. 04 Textures & Modulation (4 Presets): Analog tape hiss beds (Tape-Band Noise Floor (-42dB)), Lo-Fi Vinyl Surface Bed, Subtle Digital Dither Bed, and modular clock randomizers.
  6. 05 Performance & Layering (4 Presets): White Noise Build-Up Riser (Mod Wheel passband swell), key-triggered snare/clap burst layers, sub-bass air weight for electronic kicks, and acoustic instrument breath chiff.

Modular Power: Rear-Panel Routing & CV Matrix

Designed to integrate deeply into Reason’s modular environment, Kalibrus provides a complete rear-panel CV patchbay:

  • Pitch In & Gate In/Out: Full 1V/Oct note pitch and gate triggering. Gate Out echoes note triggers (scaled by velocity) to drive downstream envelopes or synths directly.
  • Bandwidth (Mod Wheel) CV In: Dedicated unipolar (0.0 to 1.0) modulation input allowing external LFOs or sequencers to dynamically narrow or widen the tracked passband width.
  • HPF & LPF Cutoff CV Inputs: Independent CV inputs with dedicated rear attenuator trim pots spanning up to 10 octaves for direct filter modulation.
  • Dual-Mode Level CV (VCA & Tremolo): A rear toggle selects between VCA mode and Tremolo mode. In VCA mode, accepts unipolar envelopes with positive trim opening dynamically from silence, or sidechain ducking with negative trim. In Tremolo mode, delivers clean linear amplitude modulation for bipolar LFOs.
  • Continuous Noise CV Out: Post-filter fluctuating bipolar CV output (-1.0 to +1.0) whose speed and character are sculpted directly by front-panel Noise Color and filter cutoffs.
  • Gate-Triggered Sample & Hold (S&H) CV Out: Produces stepped bipolar random CV (-1.0 to +1.0) sampled from the filtered noise bus on each incoming note strike or gate trigger, ideal for generative melodies and organic analog drift.

Under the Hood: Pure C++17 DSP Core

Under the hood, Kalibrus features a pure ISO C++17 DSP engine engineered to laboratory standards:

  • Xoshiro256++ PRNG Core: Dual independent 256-bit PRNG generators with true decorrelated stereo imaging (r < 0.005), guaranteeing mathematically pure spectral energy distribution with zero audible periodicity.
  • Cascaded 24 dB/octave Butterworth Filters: Nyquist-linearized 4th-order filter topology with zero-latency 2x polyphase oversampling, eliminating digital cramping and preserving analog-smooth filter curves up to 20 kHz.
  • True Stereo Balance Law: Employs a level-invariant True Stereo Balance law (0 dB center) with sinusoidal attenuation. Panning hard Left or Right maintains an exact -18.00 dBFS True RMS reference on the isolated channel without pan-law level boosts, making single-monitor SPL calibration straightforward.

Studio Documentation & Guides

Comprehensive operational manuals and reference guides are available: