A control circuit is configured to detect by an active filter white noise levels in detection outputs from an intermediate frequency amplifier in an FM stereo demodulation circuit so as to control the separation of outputs from the stereo demodulation circuit into left and right stereo channels, responsively to the white noise level, and is characterized in provision of a current detection circuit which is actuated by the output from the active filter and responsive to a current flowing into a resistor connected between the feedback terminal of the active filter and a reference potential point to control a blend control circuit so as to change the point whereat the separation ratio begins to vary.