PURPOSE: To eliminate a shock noise for switching by providing a bias circuit between a sound signal circuit and a changeover switch and impressing a bias voltage to a switch terminal to correct a DC operating point of the sound signal circuit in the output side.
CONSTITUTION: Input sound signals e1 and e2 are inputted to sound signal circuits 1 and 2, and output DC biases V1 and V2 are applied to a bias circuit 10 through capacitors 16 and 17. A middle voltage V4 is generated in the circuit 10 by resistances 11 and 12, and this voltage V4 is impressed to terminals 21 and 22 to be selected of a changeover switch 3 through resistances 14 and 15. By this impression of the voltage V4, the capacitor 16 is operated with a voltage (V1-V4), and the capacitor 17 is operated with a voltage (V2-V4). A coupling capacitor 18 to a sound signal circuit 4 in the succeeding stage is always operated with the level of a voltage (V3-V4) independently of the position of the switch 3, and the variation of the DC operating point of the circuit 4 is eliminated when the switch 3 is switched, and thus the occurrence of the shock noise in an output e0 is prevented.
IWAO TOYOHIRO
NAGAI HIROYUKI
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