A control-domain math block that subtracts one control signal from another. It has two control inputs and one control output, and each tick it emits the first input minus the second (a - b). There are no adjustable parameters; it is a fixed building block for combining control signals, for example to compute the difference or error between two envelopes or LFOs.
On every tick it reads both control inputs and writes their difference to the control output. One control value is produced per tick, in step with WaveWarp's sample-per-sample engine.