Echo signal processing circuit PT2399

Shown is an echo signal processing circuit PT2399. It is mostly used in digital audio processing circuits, such as karaoke circuits.
In this circuit, the microphone signal is sent to the @ pin of PT2399 through the RC coupling circuit for delay processing inside the IC. The delayed audio signal is output by
the @ pin and at the same time from the output Then take a part of the signal and send it to the @ pin through the 0 k(l resistor for secondary delay processing. This will cause
the output signal to have multiple delays. It is like the reverberation effect of the sound in the valley.