JPS5661808A - Shock noise preventing circuit - Google Patents

Abstract

PURPOSE:To prevent the shock noise, by boosting the voltage up to several-fold level by the use of the voltage of the bias circuit in an amplifier which increases gradually and thus driving the control transistor. CONSTITUTION:The capacity 28 increases up to the voltage which is decided by the resistances 36 and 37 with application of the power source. Thus the collector current increases for the transistors TR29 and 30, and then the voltage increase at the points I and H. Immideately after application of power source, the voltage is zero to turn on the TR33. And the current flowing through the resistance 38 is by-passed with no charging given to the feedback capacity 35 and the output capacity 26. And the voltage at the point J is zero. When the voltage at the point G increases with lapse of time, the emitter current of the TR33 decreases with the capacities 35 and 26 charged. And the point J increases gradually according to the voltage at the point I. The points J, H and I become steady at the prescribed level each when the charging of the capacity 28 completes. The collector voltage of the TR29 is fed back to the emitter via the TR30, and the point I has the hum eliminating function like the point H. Accordingly, the hum can be eliminated assuredly for the period from the make of power source to the steady state.