A moving fader system, primarily for the processing and combining of audio signals, includes a dedicated preprocessor to implement the execution of repetious input instructions. Other features contributing to the operation of the system include (1) "Look-up Tables" included in the preprocessor for conversion purposes, (2) a fiberoptic link for transmission of digital signals between the preprocessor and the servo circuits associated with each fader assembly, and (3) circuitry for combining the outputs of a position digital-to-analog (D/A) converter, an offset correction D/A converter and a gain correction D/A converter, to provide accurate analog servo signals to each fader assembly.