Power-balanced dynamic modeling of vactrols: application to a VTL5C3/2

Judy Najnudel (1) , Müller Remy (1) , Thomas Hélie (1) , David Roze (1)

1 S3AM - Systèmes et Signaux Sonores : Audio/Acoustique, instruMents

Vactrols, which consist of a photoresistor and a light-emitting element that are optically coupled, are key components in optical dynamic compressors. Indeed, the photoresistor's program-dependent dynamic characteristics make it advantageous for automatic gain control in audio applications. Vactrols are becoming more and more difficult to find, while the interest for optical compression in the audio community does not diminish. They are thus good candidates for virtual analog modeling. In this paper, a model of vactrols that is entirely physical, passive, with a program-dependent dynamic behavior, is proposed. The model is based on first principles that govern semiconductors , as well as the port-Hamiltonian systems formalism, which allows the modeling of nonlinear, multiphysical behaviors. The proposed model is identified with a real vactrol, then connected to other components in order to simulate a simple optical compressor.

Domaines: Modélisation et simulation; Electromagnétisme; Electronique

Judy Najnudel, Müller Remy, Thomas Hélie, David Roze. Power-balanced dynamic modeling of vactrols: application to a VTL5C3/2. 26th International Conference on Digital Audio Effects (DAFx-23), Sep 2023, Copenhague, Denmark. ⟨hal-04452215⟩