x904: VCA Gate and Expander Plugin by Antelope Audio

x904 is a recreation of a 1980s gate and expander module that was used alongside the 902 and 903 units and became a common tool in drum mixing and live sound. Antelope Audio says the developers measured a preserved unit to capture its snappy response and musical envelope behavior.

The plugin's VCA design is intended to open and close quickly while preserving the transients of the original sound. This makes it suitable for tightening drum recordings or removing bleed without dulling the attack.

Two options shape how x904 reacts to the signal. The adaptive release mode adjusts how the gate lets go, which helps with gated effects that need to follow the material. A switchable sidechain filter lets you decide which frequencies trigger the gate, so low-end or high-frequency content can be isolated from the detection.

Together these controls move the plugin beyond simple noise cleanup, allowing rhythmic gating and more deliberate envelope shaping on guitars, drums and live sources.