DSP Effects

br\u016bhi’s DSP chain processes the master mix (and per-microphone inputs on Desktop) through up to 7 effects processors. Each processor can be enabled/disabled and reordered independently.

🖥️ Desktop

The full 7-effect chain is available on the master bus and as an independent chain on each microphone slot. Effects are reorderable via drag-and-drop.

☁️ Cloud

The Cloud dashboard provides browser-side EQ and compression controls (Web Audio API). The server-side Liquidsoap chain is limited to normalize(). Full chain editing is a Desktop capability.

Effect Order (Default)

The default signal path is:

Input → HPF → LPF → 5-Band EQ → Compressor → Limiter → Noise Gate → Stereo Enhancer → Output

On Desktop, you can drag processors to a different position. The order matters: filtering before compression is almost always correct for broadcast.

Bypass Toggle

An A/B bypass button at the top of the DSP chain disables the entire chain without changing any settings. Use this for quick comparison between processed and unprocessed audio.

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1. High-Pass Filter (HPF)

Removes frequencies below the cutoff. Used to cut low-end rumble, microphone handling noise, and HVAC hum.

Parameter	Default	Range
Cutoff frequency	80 Hz	20–500 Hz
Q (resonance)	0.7	0.1–10

Tip

80 Hz is the standard broadcast cutoff. Voices contain almost no useful content below 80 Hz; cutting it reduces muddiness and leaves headroom for the compressor.

2. Low-Pass Filter (LPF)

Removes frequencies above the cutoff. Used to roll off harshness or reduce high-frequency noise.

Parameter	Default	Range
Cutoff frequency	18 kHz	1 kHz–22 kHz
Q (resonance)	0.7	0.1–10

For standard music broadcasting, leave the LPF at its default or disable it. It becomes useful when encoding at low bitrates (Opus 64 kbps, MP3 128 kbps) where high frequencies are the first to degrade.

3. 5-Band Parametric EQ

Five independent bands with full control over frequency, gain, and Q.

Band	Default Frequency	Type
Band 1	100 Hz	Low shelf
Band 2	400 Hz	Peaking
Band 3	1 kHz	Peaking
Band 4	4 kHz	Peaking
Band 5	10 kHz	High shelf

Parameter	Range
Gain	−24 to +24 dB
Q	0.1–10
Frequency	Band-dependent

Tip

For a quick broadcast voice preset: cut −3 dB at 300 Hz (reduces boxiness), boost +2 dB at 3 kHz (adds presence and clarity), boost +1.5 dB at 8 kHz (adds air and brightness).

4. Compressor

Reduces the dynamic range by attenuating signals above the threshold. Keeps loud moments from sounding jarring and quiet moments from getting lost.

Parameter	Default	Range	Description
Threshold	−18 dBFS	−60 to 0 dBFS	Level above which compression begins
Ratio	4:1	1:1 to ∞:1	How much compression is applied above threshold
Attack	10 ms	0.1–200 ms	How quickly compression engages
Release	100 ms	10 ms–2 s	How quickly compression releases
Make-up gain	6 dB	0–24 dB	Compensates for gain lost during compression
Knee width	6 dB	0–24 dB	Width of the soft-knee transition zone

The compressor uses feed-forward RMS detection with a soft-knee curve.

Tip

For music broadcasting: threshold −18 dBFS, ratio 3:1, attack 30 ms, release 200 ms, make-up +4 dB. The 30 ms attack allows transients (kick drum, snare) to pass through uncompressed, which preserves the punch of the music.

Caution

Avoid over-compression. Heavy compression (ratio above 8:1, low threshold) destroys the dynamics of music and fatigues listeners. Use the compressor to tame peaks, not to eliminate all dynamic variation.

5. Brick-Wall Limiter

The limiter is a hard ceiling that prevents any signal from exceeding the set level. It is the last line of defence before the encoder.

Parameter	Default	Range
Ceiling	−1.0 dBFS	−12 to 0 dBFS
Release	50 ms	10 ms–500 ms

The limiter uses instantaneous attack (sample-accurate) and exponential release.

Tip

Set the ceiling to −1.0 dBFS (not 0 dBFS) to provide inter-sample peak headroom, which prevents clipping in lossy encoders (MP3, AAC) even when the PCM level reads 0 dBFS.

6. Noise Gate

Silences the signal when it falls below the threshold. Used on microphones to mute background noise between sentences.

Parameter	Default	Range
Threshold	−40 dBFS	−80 to 0 dBFS
Attack	5 ms	0.1–100 ms
Hold	200 ms	0–2 s
Release	100 ms	10 ms–1 s

The gate uses a 5-stage state machine per channel: Closed → Opening → Open → Holding → Closing. The hold time prevents the gate from chattering (rapid open/close) during pauses between words.

Tip

On the master bus, the noise gate is usually not needed — it is more useful per-microphone. On the master, excessive gating can create unnatural silences between songs.

7. Stereo Enhancer

Adjusts the stereo width using a mid-side (M/S) processor.

Parameter	Default	Range	Effect
Width	1.0	0.0–2.0+	0 = mono, 1 = unchanged, >1 = wider stereo

Caution

Stereo widths above 1.5 can produce phase issues on mono listeners (e.g., AM radio, some streaming services). Check your output on a mono reference before using extreme values.

Setting width to 0.0 converts the output to mono, which is useful for testing mono compatibility or for AM transmission.