The FX Expression Generator, often shortened to Exp Gen, is an expression controller from Cooper FX. Instead of a foot rocker, it generates expression pedal movement on its own, with four assignable outputs that can each drive an expression input on another pedal. RockBoard's PedalPedia describes it as "a four output, multi-faceted expression controller perfect for adding movement and depth to your" sound1.
For a player, that means one small box can sweep the tone control on one pedal, the depth on a tremolo, and the feedback on a delay at the same time, each on its own setting1.
Controls and modes
Each of the four outputs runs in its own mode, chosen with the main soft button. RockBoard's PedalPedia lists the modes as "auto, tap, tigger, and latch"1, where "tigger" appears to be a spelling of trigger in the maker's own text.
| Mode | What the main soft button does |
|---|---|
| Auto | Runs the output automatically |
| Tap | Sets movement from taps |
| Trigger | Starts movement on a trigger |
| Latch | Holds the movement in place |
The main soft button determines what mode to run per output, so the four outputs can be set differently1.
Power
The FX Expression Generator runs on 9V DC, center negative, and draws 50mA1. That current draw is worth noting when planning a shared power supply on a pedalboard.
Where it sits on a board
Expression controllers sit apart from the effect pedals they move. The FX Expression Generator does not make sound itself; it drives the expression inputs of pedals such as filter, phaser or vibrato units that accept an expression pedal. For a broader look at the category, see Expression Pedals.
Videos
Devon Blue Whitaker (Devon Blue Whitaker music)
Sources (1)
- FX Expression Generator by Cooper FX, RockBoard PedalPedia, 2026