Sound field expanding apparatus with improved tone control system

摘要

A sound field processor having amplitude/phase conversion circuits for left and right channels of a stereophonic signal. The amplitude/phase conversion circuits for left and right channels have substantially the same circuit structure. Each of the amplitude/phase conversion circuits has an inversion amplifier, an amplitude/phase characteristic changing circuit that changes amplitude and phase characteristics of an output from the inversion amplifier, and a feedback device that add outputs from the amplitude/phase characteristic changing circuit and outputs from the inversion amplifier to an input signal to generate a sum signal and feed back the sum signal to the inversion amplifier. An output from the inversion amplifier for the left channel and an output from the amplitude/phase characteristic changing circuit for the right channel are added by a first adder device. An output from the inversion amplifier for the right channel and an output from the amplitude/phase characteristic changing circuit for the left channel are added by a second adder device. An output from the amplitude/phase characteristic changing circuit is fed back through a feedback path between an output and an input of the amplitude/phase characteristic changing circuit. A D/A converter is interposed in the feedback path to adjust the level of the feedback signal to perform bass control.