| 摘要 |
PURPOSE:To avoid the loss in the sense of distance for the sound source in a magnetic recording and reproducing unit, by suppressing the output level to the input signal more than a given level and adjusting the degree of suppression depending on the level of input signal. CONSTITUTION:When the input 11 signal V1 reaches more than a given level and the collector current ID of the transistor Tr18 is greater than the reference current Iref, the difference current ID-Iref flows to the base to turn on Tr19 and charge up the capacitor C23, allowing to suppress the level of the output signal Vo of the base 3. Further, with the increase in the charged up voltage of C23, Tr26 is turned on and small current I which is set with the resistance value of the resistor 27 flows to the collector, but since the condition of turning on Tr19 is ID>Iref+I, then the automatic level control start level is increased by the current I. Thus, at the input signal level V1 starting the automatic level control, I<<Iref is made, and around the level V2 reaching the saturation, I=1/2 Iref is taken, then the signal output by the automatic level control is increased by 3 dB to obtain the curve 50. |
