Automatic Generation of Virtual Analog Audio Plug-ins based on Wave Digital Filters

Analog audio effects can be realized as digital audio effects according to the formalism of virtual analog modeling. Among white box techniques, wave digital filters (WDFs) have lately shown to be instrumental for digitizing complex nonlinear analog circuits because they are characterized by interesting properties that allow for efficient implementations. However, building audio plug-ins requires manually designing WDFs and graphical user interfaces, tasks that are time consuming, thus hindering rapid prototyping. In this paper, the authors propose VIOLA, a framework for the automatic generation of audio plug-ins based on WDFs. Starting from a SPICE netlist, VIOLA generates an audio plug-in, taking advantage of the latest advancements in the WDF theory and of the MATLAB Audio Toolbox. In this release, the authors take into account circuits containing only diodes as nonlinear elements, but VIOLA is already structured to accommodate other nonlinearities. The proposed framework is tested for the implementation of two famous audio effects, namely the Electro-Harmonix Op Amp Big Muff Pi and the Digitech Overdrive Preamp 250, paving the way toward the fast prototyping of virtual analog audio plug-ins.