PURPOSE: To surely adjust the sound volumes and balance of two signals with a less number of parts by providing the 1st volume control element and the 2nd volume control element which changes DC voltages applied across each control electrodes of a pair of the 1st and 2nd differential transistors in reverse phases.

CONSTITUTION: When the 1st volume control element 28 is operated, the voltages applied across the 1st and 2nd electronic volumes 17 and 18 from a differential amplifier circuit 21 vary in the same direction and, as a result, the levels of the signals outputted from the volumes 17 and 18 also vary in the same direction. When the 2nd volume control element 29 is operated, on the other hand, the control voltages applied across the volumes 17 and 18 from the circuit 21 vary in a differential state and, as a result, the levels of the signals outputted from the volumes 17 and 18 vary in the opposite directions. Therefore, the number of elements, etc., required for adjusting the sound volume and balance of the two signals becomes smaller and, accordingly, the cost of this circuit can be reduced.