Sidechain
Pressure's sidechain controls let you shape what the compressor “hears” without affecting the audio output. Use them to prevent bass pumping, add frequency-conscious compression, or trigger from an external source.
Sidechain High-Pass Filter
The sidechain HPF removes low frequencies from the detector signal so bass content doesn't trigger excessive compression. This is essential on mix bus, drum bus, and any source with prominent sub bass.
On VCA, Dynamics, and VariMu engines, the TONE knob controls the HPF frequency using a quadratic curve. On FET and Opto engines, TONE serves a different purpose (FET: unused for HPF; Opto: controls emphasis).
| Parameter | Range | Notes |
|---|---|---|
| SC HPF Toggle | On/Off | Auto-enabled when TONE > ~1% |
| SC HPF Frequency | 20–300 Hz | Derived from TONE via tone² curve |
Sidechain Shelving EQ
Beyond the HPF, Pressure provides low and high shelf filters on the sidechain for more surgical frequency shaping of the detector signal.
| Parameter | Range | Description |
|---|---|---|
| SC Low Shelf Gain | ±12 dB | Boost or cut low frequencies in the detector |
| SC Low Shelf Freq | 60–400 Hz | Corner frequency of the low shelf (default 150 Hz) |
| SC High Shelf Gain | ±12 dB | Boost or cut high frequencies in the detector |
| SC High Shelf Freq | 1k–10k Hz | Corner frequency of the high shelf (default 3000 Hz) |
External Sidechain
Enable the Ext Sidechain toggle to trigger compression from an external audio source instead of the input signal. This uses a 4-channel bus (channels 3–4 carry the sidechain signal).
DAW setup: Route the trigger source to Pressure's sidechain input. In most DAWs, this is a bus/send routed to the plugin's sidechain input:
Pro Tools: Insert Pressure → click the Key Input selector → choose the sidechain source bus.
Logic Pro: Insert Pressure → click the Side Chain dropdown in the plugin header → select the source track.
Ableton Live: Set the “Sidechain” dropdown in Pressure's device view to the source track.
Reaper: Route the sidechain source to Pressure's channels 3/4 via the routing matrix.
Common Use Cases
Prevent bass pumping
Engage the SC HPF at 80–120 Hz so kick drum and bass don't trigger compression on the mix bus. TONE at ~30–50% is a good starting point.
De-essing
Boost the SC High Shelf at 4–8 kHz to make the compressor more sensitive to sibilance. Combine with fast attack for targeted sibilance control.
Frequency-conscious compression
Cut low frequencies and boost highs in the sidechain to compress based on brightness rather than overall level. Useful for taming harsh guitars or bright vocal passages.
Ducking (external sidechain)
Route a vocal to the sidechain input and compress the music bed. The music ducks when the vocal comes in — classic podcast/broadcast technique.