This circuit is an excellent application for the PIC in audio, but the reader who intends to do its assembly must be able to write the program that controls the level of the audio signals. The circuit is based on an operational amplifier that has its gain controlled externally from a voltage generated by a D / A converter. The digital signals of this circuit are generated by the PIC according to the programming given by the switches S1 and S2 used to increase and decrease the volume. The same circuit can be used for other control systems, using the output voltage of CI-3.
