To reduce switching noises and distortions by providing input terminals inputs signals of which are positive phase and antiphase, output terminals which output signals through respective resistances, resistance lines connected to the output terminals and whose respective resistance values are almost equal, switches and an operating means and performing on-off control of the switches.

Resistances 3a and 3b are connected to output terminals 2a and 2b which output complementary signals, through resistance 1a and 1b, that are positive phase and antiphase which are inputted from input terminals 1a and 1b. The resistances 3a and 3b connect each of resistance between resistances R2a to R5a and R2b to R5b, which are serially connected and whose resistance values corresponding to each other are almost equal to J-FET semiconductor switches S2 to S5. A control means changes attenuation quantity having turning change on and off the switches S1 to S5 with control signals c1 to c5 to be outputted, in accordance with the detection result of the operation of an operating means. Thus, ringing transient responses due to the level fluctuations at changing of switches with be prevented from occurring and distortion is also suppressed.