Download Optimization of Cascaded Parametric Peak and Shelving Filters With Backpropagation Algorithm Peak and shelving filters are parametric infinite impulse response
filters which are used for amplifying or attenuating a certain frequency band. Shelving filters are parametrized by their cut-off frequency and gain, and peak filters by center frequency, bandwidth
and gain. Such filters can be cascaded in order to perform audio processing tasks like equalization, spectral shaping and modelling of complex transfer functions. Such a filter cascade allows
independent optimization of the mentioned parameters of each filter. For this purpose, a novel approach is proposed for deriving
the necessary local gradients with respect to the control parameters and for applying the instantaneous backpropagation algorithm
to deduce the gradient flow through a cascaded structure. Additionally, the performance of such a filter cascade adapted with the
proposed method, is exhibited for head-related transfer function
modelling, as an example application.
Download Physical Modeling of the MXR Phase 90 Guitar Effect Pedal In this study, a famous boxed effect pedal, also called stompbox, for electrical guitars is analyzed and simulated. The nodal DK method is used to create a non-linear state-space system with Matlab as a physical model for the MXR Phase 90 guitar effect pedal. A crucial component of the effect are Junction Field Effect Transistors (JFETs) which are used as variable resistors to dynamically vary the phase-shift characteristic of an allpass-filter cascade. So far, virtual analog modeling in the context of audio has mainly been applied to diode-clippers and vacuum tube circuits. This work shows an efficient way of describing the nonlinear behavior of JFETs, which are wide-spread in audio devices. To demonstrate the applicability of the proposed physical model, a real-time VST audio plug-in was implemented.