This is digital volume control circuit that Can be applied to the normal volume of a power amplifier. When press switch S1 adds up the volume and press switch S2 to reduce the volume down.
How it works
IC1 is a 555 CMOS Timer Single IC will be connected in astable flip-flop model as pulse frequency generator up / down to input pin of the counter IC2-74LS193, through push-bottom switch S1 (Up) and S2(Down).
Changing wide of pulse signal from IC1 may replace R1 with potentiometer.
To begin with, when we press the switch S1 (increase sound) binary output will be add up and when press switch S2 (Reduce sound) the binary output will low down. The maximum counter to count to 15 (All output are logic “1” or “Higher”) and lowest is the counter 0 (All output are logic “0”).
The output ABCD of the counter IC2 will use to control both gate. Which is bipolar analog switch (IC3 and IC4 – CD4066). In either bit output are “High” logic. The resistors connected in series are the resistors R6-R9. In left signal channel and R10-R13 for right signal channel.
In this way, the control output of sound signal to the output of the power amplifier. The switch S3 is used to reset the output of the counter to 0000. For this reason, to make adjustments to the volume of both channels is low.
Parts you will need
Resistors ¼ W +-5%
R3, R4, R5__________550 ohms
R8, R12, R14, R15___4.7K
C1_________________1uF 25V Electrolytic
IC1_________________IC-7555 CMOS Timer Single 8-Pin Plastic Dip
IC2_________________IC-74193______Synchronous Up/Down 4-Bit Binary Counter with Dual Clock
IC3, IC4_____________CD4066 Quad Analog Switch/Multiplexer/Demultiplexer
S1, S2, S3 switch normally open pushbutton