Sunday, October 2, 1:30 pm — 3:00 pm (Rm 402AB)
DC coupling in audio amplifiers has been considered more dangerous than advantageous because a DC signal generated somewhere in the audio chain might damage the transducer silently. However, the transducer would benefit from a small electrical DC signal that keeps the voice coil at the desired working point in the gap and copes with the DC displacement generated dynamically by the transducer nonlinearities and a shift of the coil’s rest position due to production variances, aging, gravity, and load changes. An adaptive control system based on a nonlinear model will synthesize the DC signal automatically by minimizing the voice coil offset that can be detected from voltage and current monitoring. This technique allows to compensate for nonlinear distortion, to protect the transducer reliably against mechanical overload, and to operate the voice coil at the Bl maximum generating highest efficiency and maximal output. The workshop explains the control theory, discusses the practical implementation and illustrates the benefits and power requirements on practical demos.