This paper presents a non-linear digital implementation of the Moog ladder filter. The implementation is relatively efficient and suitable for inclusion into real-time systems, for example virtual analog synthesizers. The analog circuit is analyzed to produce a differential equation. This equation is solved using Euler’s method, and the result is shown to be equivalent to a cascade of first order IIR sections with embedded non-linearities. Finally, the filter structure is modified to improve tuning.

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