Kalibrus

Tune Your Room, Balance Your Mix, Play the Noise

Kalibrus packs three studio tools into a single 2U rack unit: a calibrated reference noise source for mixing and monitor alignment, a playable keyboard-tracked noise synth, and a dual-output random CV generator.

You can use it on the master bus to set monitor levels and balance faders, drop it into a synth stack for pitched wind leads and drum transients, or patch its rear CV outputs across the rack to add organic drift to static loops.

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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 pitch (with automatic gain compensation to keep volume steady). With front-panel continuous generation turned off, it gates and responds dynamically to note velocity, making it a fast tool for flute chiffs, wind leads, risers, or layering breathy 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 click the AUTO button. Because Kalibrus includes built-in stereo audio passthrough, you can drop it straight across a mix bus without extra mixers or splitters. It injects a warm analog noise bed while your DAW plays, and mutes itself the instant 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 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 rough static 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 moving, or crank it for generative sequencing.

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Tactile Control: Front Panel & Folded Strip

Full 2U Rack Panel

• Bay 1 (Power & Transport Sync): AUTO transport sync button (runs noise only during DAW playback), MAN manual latch button (continuous noise for room tuning), and a NOTE jewel lamp that lights on incoming keyboard notes or CV gates.
• Bay 2 (Noise Color & Spectral Sculpting): 3-way selector for active noise color (BROWN, PINK, WHITE), flanked by 24 dB/octave High-Pass and Low-Pass cutoff dials (20 Hz to 20 kHz) that enter full DSP bypass at their extremes.
• Bay 3 (Spatial Processing): 3-position routing selector ([DUAL | STR | MONO]), continuous WIDTH dial (0% to 200% with constant-power level matching), and a center-detented BALANCE control.
• Bay 4 (Noise Level & Metering): NOISE LEVEL dial with a calibrated 0 dB center detent, paired with dual vertical 20-segment Peak/RMS LED meter ladders (-48 dBFS to 0 dBFS).

Built-In Audio Passthrough & Linear Summing

Rear stereo inputs labeled Inputs (Thru Raw) let Kalibrus sit directly inline on a mix bus or synth chain without extra line mixers or spider splitters. When Kalibrus is idle, incoming audio passes through untouched at 0.0% CPU. When noise is engaged, incoming audio sums cleanly at unity gain (1:1).

Compact 1U Folded Strip

Collapse Kalibrus into a 1U strip when rack space gets tight without losing access to any front-panel controls:

• Bay 1: AUTO and MAN engage buttons, NOTE activity lamp, and patch browser buttons.
• Bay 2: Quick-select 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 horizontal stereo Peak/RMS LED meters.

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Expressive Synthesis & Keyboard Tracking

When both MAN and AUTO are off, Kalibrus sleeps at 0.0% CPU until triggered by MIDI notes or rear CV gates:

• 1V/Oct Keyboard Pitch Tracking: Play notes from a MIDI keyboard or sequencer to track Kalibrus’s filter passband across the scale (with last-note priority and pitch bend support).
• Mod Wheel & Expression Bandwidth Control: Push your Mod Wheel (CC 1), Expression Pedal (CC 11), or rear Bandwidth CV to tighten the filter passband around the played note down to a 2-semitone resonant peak, with automatic gain compensation to hold perceived loudness steady.
• Dynamic Velocity Sensitivity: Triggered notes scale with MIDI velocity and Gate CV amplitude for expressive drum layering and rhythmic accents.
• Hands-Free Sustain Latch (CC 64): Step on a sustain pedal to hold the noise voice open hands-free while tweaking controls or referencing a mix from your listening position.
• Click-Free Envelope Transitions: A 5 ms raised-cosine gate envelope prevents clicks and pops on note-on and note-off.

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35 Production-Ready Presets

Kalibrus includes 8 root Quick Starters for 1-click access, plus 27 categorized patches across 5 folders:

1. Root Quick Starters (8 Presets): Fast top-level configurations including Quick - Pink Noise, 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): K-System RMS monitoring references (K-20, K-14, Pink Stereo -12dB, True RMS Pink Reference (-18 dBFS)), AES/SMPTE Band-Limited Pink Noise (500 Hz to 2 kHz), EBU R128 (-23 dB CAL), Brown Noise Sub Reference, and mono/dual-mono phase checks.
3. 02 Mixing & Diagnostics (5 Presets): Frequency-masking mix tools and ear resets including Pink Noise Mix Balancing (-18 dB CAL), Lower-Mid Palate Cleanser (200 Hz to 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 crossover probes for Subwoofer Tuning (20 Hz to 120 Hz), Sub-Bass Room Mode Probe (40 Hz to 100 Hz), Subwoofer Crossover Alignment, and Fletcher-Munson ear fatigue checks.
5. 04 Textures & Modulation (4 Presets): Analog tape hiss beds (Tape-Band Noise Floor (-42dB)), Lo-Fi Vinyl Surface Bed (-36 dB), Subtle Digital Dither Bed (-60 dB), and Modular Clock Randomizer (S&H CV).
6. 05 Performance & Layering (4 Presets): White Noise Build-Up Riser (Mod Wheel), Snare & Clap Noise Layer (Keyed Burst), Sub-Bass Air Thump (Keyed Weight), and Acoustic Chiff & Breath Layer (Keyed).

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Modular Rear Panel & CV Patchbay

Flip the rack (Tab) for full CV modulation and gate routing:

• Pitch In & Gate In/Out Relay: Standard 1V/Oct pitch input and gate triggering. Gate Out relays incoming MIDI and CV gate pulses out to trigger external envelope generators (like Sweeper, Thor, or CV DADSR) in sync with your keyboard.
• Bandwidth (Mod Wheel) CV In: Unipolar (0V to 1V) input for sweeping passband width from an external LFO, envelope, or sequencer.
• HPF & LPF Cutoff CV Inputs: Independent cutoff CV jacks with bipolar attenuverter trim pots (±10 octaves).
• Dual-Mode Level CV (VCA & Tremolo): Switch between VCA / ENV mode (unipolar envelopes from silence to knob ceiling, plus dynamic release-tail following so external ADSR release tails aren’t cut off on key release; turn Trim negative for cubic sidechain ducking) and TREM / LFO mode (bipolar linear amplitude modulation without clipping).
• Continuous Noise CV Out: Bipolar (-1V to +1V) random control voltage tapped post-filter, so its speed and smoothness follow your front-panel Noise Color and HPF/LPF settings.
• Gate-Triggered Sample & Hold (S&H) CV Out: Latches a fresh bipolar (-1V to +1V) random voltage on every note or gate pulse.

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The Three Noise Spectra

Switch directly between three calibrated spectral slopes depending on the job:

White Noise (0 dB/octave)

Equal energy per Hertz across the full 20 Hz to 20 kHz range. Bright, crisp, and immediate. Reach for White when you’re layering snare snap and hi-hat sizzle, building synth risers, or running flat frequency-response sweeps.

Pink Noise (-3 dB/octave)

Equal energy per octave, matching how human ears perceive loudness across the frequency spectrum. Because every octave carries the same perceived weight, Pink is the studio workhorse for balancing mix faders, calibrating speaker SPL, and resetting tired ears between long mixing sessions.

Brown Noise (-6 dB/octave)

Rolls off at 6 dB per octave for deep low-frequency weight and a smooth, dark top end. Ideal for reinforcing 808s and sub-bass lines, probing room boundary resonances, and shaping warm room tone, wind, or surf beds.

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Under the Hood: Pure C++17 DSP Core

For engineers who want the exact numbers behind the faceplate:

• Dual 64-Bit Xoshiro256++ PRNG Core: Two independent 256-bit state engines (4 × uint64_t, seeded via SplitMix64 address hashing) generate uncorrelated Left and Right channels (r < 0.005) with a 2²⁵⁶ − 1 sample period and zero looping artifacts.
• Precision Spectral Shaping Filters: Pink noise uses an optimized 6-pole (+1 FIR) Paul Kellet IIR cascade (with sample-rate-adaptive sub-bass extension at 2x/4x rates) holding ±0.5 dB linearity across 20 Hz to 20 kHz, calibrated to −18.00 dBFS True RMS at the 0 dB detent. Brown noise uses a leaky integrator (10 Hz DC-blocking corner) for true −6 dB/octave sub-bass extension down to 20 Hz.
• 2x Oversampled 4th-Order Butterworth Cascades: High-pass and low-pass stages each run two cascaded 2nd-order biquads (Q₁ = 0.5412, Q₂ = 1.3066) with Nyquist-linearized pre-warping and zero-latency 2x polyphase oversampling to prevent high-frequency cramping near 20 kHz.
• Constant-Power M/S & Level-Invariant Panning: Stereo Width scales Mid/Side energy by √(2 / (1 + w²)) for unity loudness across 0% to 200%, while the 0 dB center balance law attenuates the opposite channel without boosting the active speaker during single-monitor SPL calibration.

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Studio Documentation & Guides

• Quick Start & Modulation Guide: Fast orientation and step-by-step patching recipes for Sweeper, Thor, CV DADSR, ECF-42, Matrix, and Combinator 2 rigs.
• Operation Manual & Studio Reference Guide: Full panel reference, step-by-step room calibration protocols (83 dB(C) SPL alignment, Pink Noise mix balancing, room mode probing), DSP transfer equations, and Remote maps.