This project is a compact, single-channel (mono) microphone pre-amplifier with a built-in echo/reverb effect, designed to run on a 12V power supply. Built around the popular PT2399 audio processor (U1), the board takes a microphone-level input, amplifies it, and processes it to create a classic analog echo effect. The PCB layout features a dedicated "Audio Reverb Module" section, precision 1/4W resistors, and a clean ground plane to minimize noise.

I designed this circuit to provide the DIY audio community with a reliable, easy-to-build solution for adding professional-sounding echo and reverb to microphone setups. Many digital echo modules sound sterile and complex to wire. I wanted to create a straightforward, analog-style circuit that hobbyists, makers, and audio enthusiasts can easily fabricate and integrate into their own custom microphone enclosures, karaoke machines, or guitar amplifier projects.

How does it work?

The circuit operates by taking the audio signal from the microphone and routing it through a series of RC filters and operational amplifier stages (built using the resistors R1-R5 and capacitors C1-C5). This cleans up the signal and sets the appropriate gain level.

The heart of the circuit is the PT2399 (U1), a digital delay IC that mimics analog echo. The audio signal is fed into the PT2399, where the delay time and feedback are processed to create the echo effect. The processed signal is then mixed back with the original dry signal via the output stage. The board includes a 50K potentiometer (UIR-50K) footprint for adjusting the echo mix or volume, and a dedicated 470uF/50V capacitor (C7) for stable power filtering, ensuring the 12V power supply doesn't introduce hum into the audio path.