
After several failed attempts to connect the microphone to my speaker through different methods, I decided to use the MAX9814 module as a preamplifier for the microphone signal before passing it to the PAM8403 amplifier module.
This setup brought me the closest to success yet. For the first time, the speaker responded to the microphone’s input! I could actually hear sound output as I spoke into the microphone. However, it wasn’t quite what I expected. The output from the speaker wasn’t clear audio—it was a cacophony of crackling, popping, and snapping sounds, like a series of fireworks going off. While it wasn’t what I aimed for, it was encouraging to know the system was partially working.
Determined to pinpoint the cause of the noise, I began troubleshooting. My first suspicion was that the MAX9814 module’s output signal was still too weak for the PAM8403 amplifier to process effectively. To confirm this, I measured the voltage across the MAX9814’s OUT and GND pins while speaking into the microphone. The voltage fluctuated by only 0.4V, which was far below what the PAM8403 needed for clean amplification.Unfortunately, I didn’t have any other preamplifier chips on hand to test as an alternative.
Next, I focused on the gain settings of the MAX9814. By default, the module was set to 60dB (high gain), but I wanted to see if lowering the gain could stabilize the signal. I connected the GAIN pin to VDD, reducing the gain to 40dB. The result? The speaker’s volume increased noticeably, but the crackling persisted, and the output voltage fluctuation dropped to a mere 0.01V.In addition, the voltage readings from the MAX9814 output became highly unstable, making it even harder to determine what was going wrong.
At this stage, I suspect the instability is due to one or more of the following:
- Insufficient Signal: Even with the MAX9814, the microphone signal may still be too weak for clean amplification.
- Impedance Mismatch or Noise: The connection between the MAX9814 and PAM8403 might be introducing noise or failing to match the input requirements properly.