The pre-processing stage runs before the multiband compressor and helps clean up common audio problems in your source material.
Dehummer
The Dehummer removes mains hum caused by electrical interference, ground loops, or poorly shielded audio cables. It uses a series of notch filters tuned to the mains frequency and its harmonics.
- Enabled — toggle the dehummer on or off
- Frequency — set to 50 Hz (UK/Europe) or 60 Hz (US/Canada) depending on your local mains frequency
- Q Factor — controls how narrow the notch filters are. Higher Q = narrower notch, less impact on surrounding frequencies
- Harmonics — how many harmonics to remove (1-6). Mains hum typically includes harmonics at 2x, 3x, 4x the base frequency
- Depth — how much the hum is attenuated in dB
Tip: Only enable this if you can hear hum in your source audio. The notch filters can affect tonal quality if used unnecessarily.
Declipper
The Declipper detects and attenuates clipped (distorted) audio, which can occur when your source is recorded or streamed too hot.
- Enabled — toggle the declipper on or off
- Threshold (dB) — the level at which clipping is detected. -0.5 dB is a good starting point
- Makeup (dB) — gain reduction applied after declipping to prevent re-clipping
Tip: If your source regularly clips, it's better to fix the gain staging at the source. Use the declipper as a safety net, not a permanent fix.
AGC (Automatic Gain Control)
The AGC automatically adjusts the overall input level to maintain a consistent volume before the audio reaches the multiband compressor. This is useful when your source levels vary significantly.
- Enabled — toggle AGC on or off
- Target (dB) — the desired RMS level. -18 dBFS is a good starting point
- Attack (ms) — how quickly the AGC responds to level increases (typically 500-2000 ms for smooth operation)
- Release (ms) — how quickly the AGC responds to level decreases
- Range (dB) — the maximum gain adjustment the AGC will apply (e.g. 20 dB means it can boost or cut up to 20 dB)
Tip: Use slow attack and release times for the AGC. It should gently ride the overall level, not react to individual beats or words. The multiband compressor handles the fast dynamics.
