Here is the circuit diagram of the Stereo Digital Volume Control. This circuit can be used to upgrade manual volume management in stereo amplifier circuits. In this particular circuit, pressing switch S1 controls forward (volume up) operation of both channels, while the same switch S2 controls reverse (volume down) operation of both channels.
In this digital volume control circuit, IC1 timer 555 is set as an astable trigger by pressing on switches S1 and S2. To adjust the pulse width from IC1, you can use a variable resistor instead of timing resistor R1.
Operation of switch S1 (up) triggers the binary output to increase, while operation S2 (down) triggers the binary output to decrease. The highest count is 15 (all outputs logic 1) and the lowest count is 0 (all outputs logic 0), which outputs the highest and lowest volume respectively.
The counter’s active-high outputs A, B, C, and D are used to control two quad bipolar analog switches in each of the two CD4066 ICs (IC3 and IC4). These two output bits, when high, short-circuit part of a resistor network consisting of series resistors R6 to R9 on one channel and R10 to R13 on the other channel to manage the output of the audio signal fed to the input. Stereo amplifier circuit module. Pressing switch S3 is used to reset the output of the counter to 0000, thereby turning the volume of the two channels to the minimum level.