Wide range audio frequency oscillator BA546
In this project, we're going to build a low-frequency oscillator that can generate a sound at any pitch, high or low. You can hear the generated sound by amplifying it with the audio power amplifier IC.
As you'll see in the schematic, the oscillating circuit is an astable multivibrator using the NAND IC. Its frequency is determined by C1 and 100K control volume (and R2). When the resistance of the 100K control volume is increased to the maximum, the frequency is about 200 Hz. When its resistance is reduced to the minimum, the frequency goes up to about 12 kHz.
This circuit is a square-wave oscillator. When you finish making all wiring connections, rotate the 50K control volume fully counterclockwise, and turn power ON.
Then, rotate the 50K control volume clockwise, and you'll hear a sound generated from the astable multivibrator. Now rotate 100K control volume and see how the pitch of the sound changes.