Intercom Arduino, A6 Module With Amplifier

In this Intructable I showed how to make an intercom based on an Arduino and an A6 module.

However, the sound output was not loud. My brother, who uses the intercom, asked me to amplify the sound from the A6 module. So, I tried to insert an amplifier between the A6 module and the speaker.

The program was simplified, see my Github.

I am not familliar with sound and amplification and I tried several amplifiers, like the LM386 etc. However, without success.

I saw that most sound sources and amplifiers use a ground (-) and a positive (+) output, but when I measured the voltage of the REC- and REC+ of the A6 module, I found out that these are both positive, about 1.5 V. Apparently this voltages fluctuates a bit to generate the sound and no ground is used.

I therefor tried to amplify the fluctuations in both voltages, with success. I found out that a cheap PAM8403 amplifier works fine. See the picture for the connection scheme.

I had some space in the intercom and extended the PCB, glued it by hot glue.

The amplifier needs 5V, which already was present in the intercom. I used a large capacitor to improve sound and stability.

The amplifier board was connected via bent male header pins.

Adjust the potentiometer to find the optimal amplifier setting.

After closing the box, the amplifier is unvisible, but audible.