The project used interesting approach for reducing speaker distortion and increasing bass response. A dual coil speaker driver is used but only one of the coils is connected to the power amplifier – the other is used for electromotive feedback. This method is not new, but is difficult to implement in pure analogue world because of the many parameters that have to be tuned. For easier experimenting and tuning, a dsPIC30F2020 device is used.
It not only implements a Proportional-Integral-Derivative controller for the feedback, but with its powerful SMPS controller and ADC drives a ClassD amplifier for the subwoofer! This type of amplifier, called also “digital” amplifier uses pulse-width modulation (PWM) to drive power transistors in switching mode. The main benefit is the losses are very small compared to the ClassAB power amplifier. The heat dissipated and more power can be transferred to the speaker driver with only small heatsinks used. The project designed by Alexander Popov & Jordan Popov.
Digital Subwoofer Amplifier
Download Project Documentation (zip)