MUTING CIRCUIT FOR AUDIO DEVICE

摘要

PURPOSE:To obtain the sufficient muting effect to both the positive and negative input pulse by applying both the NPN- and PNP-type transistors to control the input signal at the input signal line to the main amplifier. CONSTITUTION:The signals branched off from input signal line 1 are supplied to the collector to which NPN- and PNP-type transistors Tr2 and 3 are connected in common. The emitters of Tr2 and 3 are grounded. Furthermore the anode of Zener diode 4 is connected to the base of Tr2; the cathode of Zener diode 7 is connected to the base of Tr3; the other end of diodes 4 and 7 each is connected to the emitter and the collector of driving Tr5; and both the positive and negative voltage of DC voltage are applied to the bases of Tr2 and 3 each. And when the muting control signal features zero. Tr5 is cut off by the discharge current of the delay circuit with application of the forward bias to the bases of Tr2 and 3. Thus the conduction is secured for both Tr2 and 3, ensuring an effective muting to both the positive and negative pulses.