Tone control device and sound volume/tone control device for reducing noise at the time of tone modification

摘要

A volume/tone control circuit comprises first and second latch circuits (8) and (9) for latching the volume control data BD and the tone control data TD stored in the shift register (7); a volume regulating circuit (2) and a tone regulating circuit (3) for regulating the volume and the tone of the input audio signal according to the respective output data of the first and second latch circuits (8) and (9); and a zero- crossing detection circuit (12) for detecting zero- crossings of the input signal. The input audio signal is fed to the zero- crossing detection circuit (12) when a data detection circuit (20) detects that the input data and the output data of the first latch circuit (8) differ. The output audio signal of the tone regulating circuit is fed to the zero- crossing detection circuit (12) when the input data and the output data of the second latch circuit (9) differ and they control data of either the first latch circuit or the second latch circuit is updated in response to the detection output of the zero- crossing detection circuit.