Mixer & EQ

Channel Strip

Each deck has an independent channel strip with this signal flow:

Source → Trim → EQ → Color FX → Effects → Fader → Analyser → Crossfader Gain → Master
                                    ↓
                              CUE Gain → Headphone Bus (pre-fader)

Layout

The mixer is a 3-column CSS grid: Deck A (left), center icons, Deck B (right). From top to bottom:

Section	Control	Range
Gain trim	Knob (bipolar)	-12 to +12 dB
HI EQ	Knob + Kill button	±range (configurable)
MID EQ	Knob + Kill button	±range
LOW EQ	Knob + Kill button	±range
Color FX	Knob (bipolar)	-1 to +1
Volume	Vertical fader (140px)	0 to 1
VU Meter	12-segment LED column	Per-deck

Deck A controls read left-to-right (value → knob → kill), Deck B is mirrored (kill → knob → value).

EQ Models

Three models selectable in Settings, hot-swappable at runtime. See Architecture for exact crossover frequencies.

LR4 Isolator (Default)

Linkwitz-Riley 24 dB/oct parallel isolator. Crossovers at 250 Hz and 4000 Hz. Each band is fully independent — killing one band has zero effect on the others.

DJ Peak (Pioneer DJM-style)

Serial shelving/peaking EQ at 80 Hz / 1 kHz / 12 kHz. No kill capability — this model trades isolation for a smoother, more musical response.

Xone Kill (Allen & Heath-style)

48 dB/oct full-kill isolator. Crossovers at 200 Hz and 2500 Hz. Slight resonance (Q=1.0) at crossover points gives a characteristic bump.

Kill Switches

On isolator models (LR4, Xone), when the EQ knob reaches the minimum of its range, the band gain snaps to 0 (true silence). This is a hard kill, not a fade — the transition is instant.

Color FX

Bipolar filter sweep from -1 to +1:

• Negative: Lowpass — sweeps from 20 kHz down to 20 Hz
• Zero: Bypass (20 kHz, fully open)
• Positive: Highpass — sweeps from 20 Hz up to 20 kHz

Frequency follows an exponential curve: 20 × 1000^|knob|. Q increases toward the extremes for more aggressive filtering.

Volume Fader

140px vertical fader, range 0 to 1. The volume LCD below shows dB: values below -60 dB display as "-∞".

VU Meters

Per-Deck Meters

Property	Value
Measurement	RMS (√mean of squares × 1.414 scaling)
Segments	12
Width	6px per column
Colors	Segments 0–7: green, 8–9: amber, 10–11: red
Attack	Instant (0 ms)
Release	Logarithmic decay, factor 0.88/frame (~150 ms to half)
Peak hold	1000 ms, then decays
Update rate	~30 fps (direct DOM, no React re-renders)

The 1.414× scaling (√2) ensures a full-scale sine wave reads ~1.0 on the meter.

Master VU Meter

Center column, 2 columns (L/R) × 12 segments × 5px width. Same color scheme as deck meters but with 0.3 off-opacity (vs 0.5 for decks). No ballistics — raw level applied directly.

Known Issue

Both L and R columns read the same levels.master value — true stereo metering is not implemented on the master bus.

Crossfader

Horizontal fader (260px), labeled A (left) and B (right). Position 0 = full Deck A, position 1 = full Deck B.

Curves

Curve	Formula	Character
Smooth (default)	cos(pos × π/2) / sin(pos × π/2)	Equal-power, no center dip
Sharp	Cubic (1-x)³ / x³ over 0.02–0.98, with 2% dead zones	Both full at center, fast cuts

Headphone Cue

Pre-fader listen (PFL) — taps signal after effects but before the volume fader.

Controls

Control	Function
CUE A / CUE B	Toggle pre-fader listen per deck
Mix knob	Blend CUE ↔ Master (equal-power cosine crossfade)
Volume	Headphone output level
Split	L = CUE, R = Master (mono sum each side)

Split mode crossfades over 10 ms to prevent clicks when toggling.

Phase Meter

Located in the mixer HUD (tabbed with SCOPE). Shows beat phase alignment between decks:

Zone	Delta	Color	Visual
LOCKED	< 2 ms	White	No label
NEAR	2–10 ms	Green	"+5ms"
WARN	10–30 ms	Amber	"-15ms"
CRIT	> 30 ms	Red	Shake animation

HP / Master EQ Strip

Toggle between two panels below the crossfader:

HP Panel: CUE A button, Mix knob, Split toggle, Volume knob, CUE B button

Master EQ Panel: Low (80 Hz) / Mid (1 kHz) / High (12 kHz) shelf knobs, ±12 dB

Effects

Architecture

Effects are parallel sends off a shared filter merge bus, not serial. Each effect has an independent wet gain summed into a gate node before output.

Input → Filter (inline LP/HP) → Filter Merge
    ├── Dry (gain-compensated) ──────────────┐
    ├── Delay send ──────────────────────────┤
    ├── Reverb send ─────────────────────────┤
    ├── Phaser send ─────────────────────────┤
    ├── Flanger send ────────────────────────┤
    ├── Crusher send ────────────────────────┼→ Gate → Output
    ├── Echo send ───────────────────────────┤
    ├── Tape send ───────────────────────────┤
    └── Noise (independent source) ──────────┘

Gain Compensation

Dry gain is dynamically adjusted based on active wet sends:

dryLevel = 1.0 / (1.0 + sumOfAllWetGains)

This prevents volume stacking when multiple effects are active simultaneously.

Parameter Smoothing

All AudioParam changes use setTargetAtTime() with τ = 12 ms. Changes smaller than 1×10⁻⁶ are skipped.

Effect Reference

FLT — Bipolar Filter (Inline)

Parameter	Range	Notes
Amount	0–1 (mapped to -1..+1)	Negative = LP, Positive = HP
Frequency	20 Hz – 20 kHz	`20 × 1000^
Q	1 (default), max 4	Tapered toward extremes

Not a send — processes inline before all other effects.

DLY — Tempo Delay

Parameter	Range	Notes
Wet	0 – 0.6	amount × 0.6
Feedback	0.3 – 0.65	0.3 + amount × 0.35
Time	BPM-synced	Dotted 8th: (60/BPM) × 0.75

REV — Reverb

Parameter	Range	Notes
Wet	0 – 0.5	amount × 0.5
IR duration	1.2s	Synthetic noise decay (x³ envelope)
IR	Shared	Single buffer across all decks (saves 211 KB)

PHA — 4-Stage Phaser

Parameter	Range	Notes
Wet	0 – 0.7	amount × 0.7
LFO rate	0.2 – 2.2 Hz	0.2 + amount × 2
LFO depth	400 – 1600 Hz	400 + amount × 1200
Stages	4	Allpass chain, Q=5

FLG — Flanger

Parameter	Range	Notes
Wet	0 – 0.6	amount × 0.6
LFO rate	0.1 – 1.6 Hz	0.1 + amount × 1.5
LFO depth	1 – 5 ms	0.001 + amount × 0.004
Feedback	0.3 – 0.6	Capped to prevent resonance > 0 dB
Base delay	5 ms	Reset to 3 ms on activation

GATE — Beat-Locked Chop

Parameter	Values	Notes
Divisions	1/32, 1/16, 1/8, 1/4, 1/2	Amount selects index 0–4
Duty cycle	70% open / 30% closed	Fixed
Ramp	2 ms attack, 5 ms release	Prevents clicks
BPM sync	Yes	Locked to beat grid

CRU — Bitcrusher

Parameter	Range	Notes
Wet	0 – 0.7	amount × 0.7
Steps	16 (mild) → 3 (harsh)	16 - amount × 13
Curve	4096-sample staircase	Regenerated only when step count changes

ECH — Dub Echo

Parameter	Range	Notes
Wet	0 – 0.5	amount × 0.5
Time	BPM-synced	Half beat: (60/BPM) × 0.5
Feedback	0.4 – 0.7	Capped from 0.85 to prevent low-freq buildup
Filter	3000 → 800 Hz LP	In feedback loop — progressive darkening
Filter Q	0.5	Fixed

TAPE — Tape Stop

Stub Effect

TAPE is a non-functional stub. The implementation is a single GainNode with wet gain up to 0.4 — no filter, no pitch manipulation, no playback rate change. It simply mixes a gained copy of the dry signal, causing a slight volume boost rather than a tape stop effect.

NOISE — White Noise Sweep

Parameter	Range	Notes
Wet	0 – 0.35	amount × 0.35
Filter	200 – 12000 Hz LP	200 + amount × 11800
Filter Q	1 – 4	Capped at 4 to prevent violent transients
Source	Independent	2s looping noise buffer (shared, saves 352 KB)

Not sourced from audio input — generates its own white noise.

Recording

Format

Property	Value
Format	WAV (32-bit float PCM, stereo)
Sample rate	Matches AudioContext (44,100 Hz)
Tap point	Post-limiter master bus output

Architecture

Crash-proof design using SharedArrayBuffer ring buffer (131,072 frames, ~3 seconds at 44.1 kHz). Audio flows: MasterBus.output → recording-tap AudioWorklet → SharedArrayBuffer → Electron IPC → fs.writeSync.

Fixed ~1 MB RAM regardless of recording length.

Features

• Start/stop/cancel recording
• Save As via native dialog
• Orphan recovery (temp files from crashes survive on disk)

Electron Only

Recording requires the Electron desktop app with SharedArrayBuffer support. Not available in browser-only mode.