Download Antialiasing in BBD Chips Using BLEP Several methods exist in the literature to accurately simulate Bucket
Brigade Device (BBD) chips, which are widely used in analog
delay-based audio effects for their characteristic lo-fi sound, which
is affected by noise, nonlinearities and aliasing. The latter is a desired quality, being typical of those chips. However, when simulating BBDs in a discrete-time domain environment, additional aliasing components occur that need to be suppressed. In this work, we
propose a novel method that applies the Bandlimited Step (BLEP)
technique, effectively minimizing aliasing artifacts introduced by
the simulation. The paper provides some insights on the design
of a BBD simulation using interpolation at the input for clock rate
conversion and, most importantly, shows how BLEP can be effective in reducing unwanted aliasing artifacts. Interpolation is shown
to have minor importance in the reduction of spurious components.
Download A Clipping Prevention Method for All-Pass Digital Filters with Time-Varying Coefficients A clipping prevention method is proposed for first- and second-order all-pass filters with time-varying coefficients. Unlike conventional anti-clipping or declipping approaches, the method operates directly on the coefficient dynamics and does not rely on assumptions about internal energy evolution, by just asking that the input signal is not already clipping. The core idea is to control the deviation between the output of the time-varying filter and that of an equivalent static all-pass structure with constant coefficients. By adaptively limiting this deviation at runtime, the output is constrained below a prescribed clipping threshold (typically unit magnitude). The method is active only during short transients where clipping would occur, after which the coefficients are released to reach their target values. This preserves the integrity of the input signal and the numerical properties of the all-pass filter. Experimental results confirm the expected behavior even in scenarios where energy-preserving all-pass structures exceed the clipping threshold, suggesting the proposed approach as a practical solution for robust dynamic filter implementations with limited additional computational cost, suitable especially for embedded digital audio processing hardware.