SOUND SIGNAL REPRODUCTION CIRCUIT AND NOISE CANCELING HEADPHONE CIRCUIT

PROBLEM TO BE SOLVED: To reduce increase in current consumption of an amplifier circuit due to a level of a received sound signal and can supply an input audio signal to a speaker or the like even when a power supply voltage is decreased resulting in deactivating the amplifier circuit without the need for a changeover circuit. SOLUTION: In the noise canceling headphone circuit where an audio signal from an audio signal input terminal 1 is fed to an input of the amplifier circuit 3 via a level adjustment device 22, a surrounding sound signal from a microphone 6 is fed to the input of the amplifier circuit 3 via a filter 7 adjusting a phase and a level of the surrounding signal, an output signal from the amplifier circuit 3 is fed to one input terminal of an adder circuit 24, the audio signal from the audio signal input terminal 1 is fed to the other input terminal of the adder circuit 24 via a resistor 25, and an output signal from the adder circuit 24 is fed to the speaker 5, the signals with the same level are given to the one input terminal and the other input terminal of the adder circuit 24.