I've made a project centred around the XS3868 module which is based on OVC3860. The circuit works fine and I was able to get the microphone to work except for just one thing, the mic input is noisy as hell. The audio input is clear enough when I'm speaking something to the mic, but it gets noisy in an echoing manner whenever there is silence.
I want to get rid of this distracting noise. Is there any way to do so? If so, then please help me in making my project reach closer to perfection.
Here is the schematic which I followed:
The schematic is simply based on the manufacturer's application schematic. I'm a beginner with digital signals and hence I simply combined multiple schematics into one. However, I'm ready to learn and improve this schematic.
The details about my microphone connections are as follows:
- My circuit uses the microphone of TRRS earphones.
- The mic input is fetched through the MIC and GND ring and sleeve.
- Since XS3868 has different GND pads for audio and power supply, therefore, instead of grounding one of the mic terminals according to the schematic, I connected it to AGND, or the Audio-Ground pad, of XS3868. AGND is at around 0.6V voltage level.
This connection to AGND is indirectly made because I also use the earphones inserted to the TRRS jack for audio output and earphones intrinsically connect MIC- to GND. This has been done to prevent shorting AGND with GND.
What I've Tried
I tinkered around with the circuit and here's what I've observed:
- Connecting an external condenser microphone according to the schematic(which is based on the manufacturer's schematic), i.e. with MIC- grounded properly, I still heard the noise, which subjectively felt slightly lesser in magnitude.
Recording of the noise: https://clyp.it/gap2kc0z