Audio Preamplifier with Digital Volume

The circuit is a preamplifier with digital regulation intensity of sound. He is separated in three departments. In first schematic (Fig.1), is found the circuit of control of electronic potesometer. The control become from two pressing switches. The S1 (UP), that put up the intensity of sound and the S2 (DOWN), on the contrary, that lower the intensity, checking them two oscillator follow a bistable multivibrator R-S (ICIC-D), with that determined the direction of counter IC3.. The gate IC2B ensure deactivate the counter in the limits of region of regulation. With the S4 we have the possibility selecting the level of sound, in which it will come back after RESET or when we give supply in the circuit. This operation is very useful when we select null level of sound, then with switch S3 we have the possibility of going to situation MUTE, to rapid nihilism of sound.

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