Oscillator using power amplifier IC BA546
Here's another audio oscillator using the audio power amplifier IC, but it's a bit different because it can produce two kinds of sound, high- and low-pitched, by changing the position of the key.
Since we use the power amplifier IC to build this project, this oscillator can produce a very loud sound. The frequency is determined by R1 and R2 when S1 is OFF, and by R1, C1 and C2 when S1 is ON.
When you finish wiring up the project, turn power ON and see how it makes two kinds of sound. You'll see that it makes a high-pitched sound when S1 is OFF. The frequency at this time is about 5 kHz.
Turn S1 ON and the pitch goes down. That's because the frequency goes as low as about 500 Hz when S1 is turned ON.