The XT-EG Expander / Gate is Harrison's versatile tool for gating noise, or gently increasing the dynamic range of tracks.
The sound of the XT-EG was derived from Harrison's many years of developing high-end music and film tools. Like all XT plugins, the goal is to fix problems in your tracks without any unwanted artifacts. Providing an "effect" is easy; the goal of the XT series is to fix tracks without anyone knowing they needed to be fixed.
All of the common gate controls are accounted for - Depth, Hold, Attack, Release - but there are also some not-so-common tools that are typically reserved for high-end audio gear:
A Hysteresis control allows the gate to open at one level, and remain open even if the signal drops slightly below the original threshold. This can avoid chattering if the signal is very near the noise threshold.
The Lookahead control can help better prepare the gate for opening, as the plug-in can be set to see waveforms just before they reach the playhead. Adjustable times of 0ms, 5ms, and 20ms give you the freedom to gate percussive transients without creating unpleasant distortion.
The Sidechain Filter allows you to focus on a particular frequency for the gate's detector. This can be helpful when you are trying to zero in on a particular instrument of a multi-mic recording, and is especially helpful when gating close-miced drums.
The Expander section features controls for Ratio and Knee. The Expander is useful for gently increasing the dynamic range on tracks that don't require noise gating.