Documentation Index
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NEON DJ’s signal processing chain gives every deck six rotary knobs — three EQ bands, a morphing filter, an echo send, and a reverb send — all wired as live Web Audio API nodes so changes are instantaneous and glitch-free. Below the decks, a row of seven FX pads trigger dramatic one-shot and momentary effects routed directly to the master bus.
The Six Knobs Per Deck
Each deck has a row of six knobs rendered as 42 × 42 px circular elements. The indicator line starts at center (12 o’clock) and sweeps ±135° across a 270° arc.
Knob Interaction
- Click and drag vertically to change a value: dragging up increases it, dragging down decreases it. The sensitivity is
120px of drag per full range travel.
- Double-click any knob to instantly reset it to its default (center) value.
- Values are shown in a small numeric readout below each knob label.
Double-clicking any knob resets it to its center/default value. This is the fastest way to undo an EQ boost or kill a filter sweep mid-mix.
HIGH — High-Shelf EQ
| Property | Value |
|---|
| Web Audio node | BiquadFilterNode, type highshelf |
| Shelf frequency | 3 800 Hz |
| Range | −26 dB to +12 dB |
| Default | 0 dB (unity gain) |
MID — Peaking EQ
| Property | Value |
|---|
| Web Audio node | BiquadFilterNode, type peaking |
| Center frequency | 1 000 Hz |
| Q | 0.9 |
| Range | −26 dB to +12 dB |
| Default | 0 dB |
LOW — Low-Shelf EQ
| Property | Value |
|---|
| Web Audio node | BiquadFilterNode, type lowshelf |
| Shelf frequency | 200 Hz |
| Range | −26 dB to +12 dB |
| Default | 0 dB |
LOW to minimum) while bringing in the other deck’s bass, then swap. Because both use independent BiquadFilterNode instances, neither deck’s EQ affects the other.
FILTER — Morphing High/Low-Pass
| Property | Value |
|---|
| Web Audio node | BiquadFilterNode (type changes dynamically) |
| Knob range | −1.0 to +1.0 (internal) |
| Default | 0.0 (open / flat) |
| Display label | OFF at center, LP when negative, HP when positive |
- Center (|value| < 0.03): Filter type is
lowpass with cutoff at 22 000 Hz and Q ≈ 0 — effectively transparent.
- Left half (value < −0.03): Switches to
lowpass, Q = 4. Cutoff sweeps from ~8 000 Hz down to 200 Hz as you rotate left. Useful for dark, muffled buildups.
- Right half (value > 0.03): Switches to
highpass, Q = 2. Cutoff sweeps from ~190 Hz up to ~5 040 Hz as you rotate right (formula: 40 + v × 5000 Hz, where v starts at 0.03 just past the dead zone). Creates the classic filter sweep DJ effect.
ECHO — Delay Send
| Property | Value |
|---|
| Web Audio node | GainNode (send) → DelayNode → feedback GainNode loop |
| Delay time | Calculated as (60 / baseBPM) * 0.75 seconds (dotted eighth note) when a track is loaded; default ~0.35 s |
| Feedback | 0.38 |
| Wet send scaling | knobValue * 0.85 |
| Knob range | 0 – 1 (displayed as 0 – 100) |
| Default | 0 (dry) |
channelGain through a GainNode (the send level) into a DelayNode, which feeds back into itself via a gain of 0.38. The delay output rejoins the signal chain at crossGain, so the echo is also subject to the crossfader. Raising the knob blends in a musical dotted-eighth delay — it doesn’t replace the dry signal, it adds to it.
REVERB — Convolver Send
| Property | Value |
|---|
| Web Audio node | GainNode (send) → ConvolverNode |
| Impulse response | 1.8 s synthetic room tail (decaying stereo noise buffer) |
| Wet send scaling | knobValue * 0.9 |
| Knob range | 0 – 1 (displayed as 0 – 100) |
| Default | 0 (dry) |
ConvolverNode loaded with a procedurally generated impulse response: 1.8 seconds of stereo white noise multiplied by a (1 − i/len)^2.5 decay envelope. The impulse response is generated once and shared by both decks. Raising the REVERB knob sends the post-channel-fader signal into the convolver, adding a lush room tail without affecting the crossfader balance.
Signal Chain
Each deck’s audio flows through the following fixed chain before reaching the master:
AudioBufferSourceNode
→ eqLow (lowshelf, 200 Hz)
→ eqMid (peaking, 1 kHz)
→ eqHigh (highshelf, 3.8 kHz)
→ filter (lowpass/highpass morphing)
→ channelGain ← channel fader controls this
├─ → delaySend → delay → feedback loop ─┐
├─ → reverbSend → convolver │
└─ → analyser (VU meter source) │
→ crossGain ← crossfader controls this │
↑─────────────────────────────────────┘
→ masterGain → masterLimiter → AudioContext.destination
Channel Fader
Each deck has a vertical channel fader (<input type="range" class="chfader">) in the center mixer panel, range 0 – 100 (default 100). It directly sets channelGain.gain.value (as faderValue / 100). Deck A’s fader is colored magenta, Deck B’s is cyan via accent-color.
The channel fader controls the individual deck volume before the crossfader. Setting a channel fader to zero silences that deck regardless of crossfader position.
Crossfader
The horizontal crossfader slider (<input type="range" class="cross">) spans the full width of the center mixer panel, range 0 – 100, default 50.
The crossfader uses an equal-power curve so the perceived loudness stays constant as you sweep across:
const x = crossfader.value / 100; // 0..1
const gainA = Math.cos(x * 0.5 * Math.PI); // 1 at x=0, 0 at x=1
const gainB = Math.cos((1 - x) * 0.5 * Math.PI); // 0 at x=0, 1 at x=1
| Position | Deck A Volume | Deck B Volume |
|---|
| 0 (full left) | 1.0 (full) | 0.0 (silent) |
| 50 (center) | ~0.707 (−3 dB) | ~0.707 (−3 dB) |
| 100 (full right) | 0.0 (silent) | 1.0 (full) |
← and → move the crossfader by 5 units per press.
Master Volume
The master volume knob is a horizontal range input (<input class="mvol">, range 0 – 100, default 85) in the header strip. It sets masterGain.gain.value directly. The master limiter (a DynamicsCompressorNode with threshold −3 dB, ratio 20:1) sits downstream and prevents clipping when multiple loud sources play simultaneously.
FX Pads
The FX bar runs below the console and contains seven pads. All effects play through masterNode() — the master gain bus — so they’re heard regardless of crossfader or channel fader position.
FX pads can be triggered with keyboard keys 1 – 7 as well as mouse clicks. See the Keyboard Shortcuts page for the full binding list. | Pad | Key | Duration | Description |
|---|
| ⬆ RISER | 1 | 2.2 s | Band-pass filtered noise sweep (300 Hz → 9 kHz) layered with a sawtooth oscillator rising from 200 Hz to 2 000 Hz. Both fade in over 2.2 s and cut off sharply. |
| 📢 AIRHORN | 2 | 1.1 s | Four detuned sawtooth oscillators forming a chord (semitones 0, 0.5, 7, 7.5 above 233 Hz). Frequency slides slightly sharp at the start then settles. Filtered through a 3 500 Hz low-pass. |
| 💥 IMPACT | 3 | 1.6 s | Sine wave falling from 220 Hz to 28 Hz (body hit) layered with low-pass filtered noise sweeping 6 kHz → 200 Hz (the transient crack). Both decay exponentially over 1.6 s. |
| ⚡ ZAP | 4 | 0.4 s | Square oscillator pitch-drops from 1 800 Hz to 120 Hz in 0.4 s with a fast fade-in and exponential fade-out. |
| 🌀 FLANGER | 5 | 3.3 s | Momentary flanger: ramps the master flanger wet-send from 0 to 0.85 in 0.1 s, holds for 2.6 s, then fades to 0 over the final 0.7 s. The flanger LFO runs at 0.35 Hz with a 5 ms delay and 0.55 feedback. |
| 🛑 TAPE STOP | 6 | ~0.7 s | Tape-stop effect: ramps playbackRate of every playing deck to 0.001 over 0.7 s, then pauses those decks. Useful for a dramatic full-stop moment. |
| 🔊 ECHO | 7 | 2.6 s | Momentary echo throw: ramps the master echo wet-send to 0.6 in 0.05 s, holds for 2.0 s, then fades out over 0.6 s. Uses the same 0.34 s delay with 0.45 feedback as the per-deck echo. |
Riser — Technical Detail
noise buffer (3 s)
→ BiquadFilter (bandpass, Q=8)
frequency: 300 Hz → 9000 Hz (exponential, 2.2 s)
→ GainNode: 0 → 0.5 (ramp), then 0 (cut)
→ masterGain
OscillatorNode (sawtooth)
frequency: 200 Hz → 2000 Hz (exponential, 2.2 s)
→ GainNode: 0 → 0.12 (ramp), then 0 (cut)
→ masterGain
Airhorn — Technical Detail
[4 × OscillatorNode (sawtooth), semitones 0/0.5/7/7.5 above 233.08 Hz]
each: frequency slides from base*0.96 → base in 0.12 s
→ BiquadFilter (lowpass, 3500 Hz)
→ GainNode: 0 → 0.22 (0.04 s), hold, → 0 (0.2 s tail)
→ masterGain