Abstract: A reverb generator comprises a delay circuit for delaying an input audio signal, a feed back path connecting an output port of the delay circuit to its input port, and a phase shifter connected in series to the delay circuit. The phase shifter produces a dispersion in the spectrum of the input audio signal in accordance with frequency dependent delay characteristic in such a manner that the delay time is large in a low frequency range and small in a higher frequency range. By including the phase shifter in the feed back path, one can obtain an output audio signal having a spectrum which is repeatedly subjected to dispersion, thus simulating the effect of dispersion due to the multiple reflections taking place in an actual concert hall.

Abstract: A multi-channel reproducing system comprises main speakers for sounding an input audio signal as a main channel audio signal, a phase shifter supplied with the input audio signal for shifting a phase thereof, and sub-speakers supplied with an output signal from the phase shifter as a sub-channel audio signal for sounding the sub-channel audio signal. The phase shifter has a frequency versus delay time characteristic in which a delay becomes large as the frequency decreases and small as the frequency increases.

Abstract: An audio signal amplifier for an electromagnetic transducer, comprises a transformer which has a primary winding coupled to the electromagnetic transducer for receiving an output audio signal from the electromagnetic transducer and a secondary winding for producing a transformed audio signal as an output. The transformer has a turn ratio of the primary winding and the secondary winding which is selected to n:1, where n is a real number greater than 1. The audio signal amplifier further comprises a current-voltage conversion circuit which is coupled to the secondary winding of the transformer for converting an audio signal current from the secondary winding into an audio signal voltage.