Analyzing the Moog VCF with Considerations for Digital Implementation

Various alternatives are explored for converting the Moog four-pole Voltage Controlled Filter (VCF) to discrete-time form for digital implementation in such a way as to preserve the usefulness of its control signals. The well known bilinear transform method yields a delay-free loop and cannot be used without introducing an ad-hoc delay. Related methods from digital control theory yield realizable forms. New forms motivated by root locus studies give good results.