WTV020M01 : MP3 to compatible WAV

I tried to use the WTV020M01 and an ESP8266 to create a connected speaker.

Unfortunately, the WTV020M01 module seems to only accept AD4 audio files, and some WAV files with limitations.
I discovered another module to play sounds, the DFPlayer Mini.
In the meantime, I still want to use my WTV020.
As the AD4 format is proprietary and not used anymore, I had to learn how to convert a MP3 file into a WAV file with compatible characteristics.

The module supports WAV file formats with sampling rates from 6Khz to 16Khz. It's less than the AD4 format, but with a little speaker I don't think it will matter.

Before editing the MP3 files, it's mandatory to properly format your SD card.

Format SD Card

Important remark: As the module is cheap and old, only non-HC SD micro-cards can be used. Basically, any card below 2GB should be OK.
And even with that, some folks had to add a power supply wire directly on the SD card.

The SD-card has to be formatted with the software from the SD Association:

SD Formatter

Convert audio files


For this process, I use Audacity (Open Source)


  1. Open Audacity
  2. Open your audio file
  3. Select "Tracks" -> "Stereo Track to mono"
  4. Click on the name of your track, and select "Set sample format" -> "16-bit PCM"
  5. On the bottom of the screen, "Project Rate (Hz)" -> 16000
  6. Menu "Effect" -> "Amplify", choose a value to have a sound below the 0.5 graduation
  7. Menu "File" -> "Export audio...", and select "Type": "WAV (Microsoft) signed 16 bit PCM"

Now I just have to copy the files at the root of the SD card, with filenames as 0000.wav, 0001.wav, 0002.wav, ..., 0009.wav, 0010.wav...


  1. Format the SD card with the official tool
  2. Rework your audio files to get "wav" (PCM 16bits) mono / 16kHz file;
  3. Copy the audio files on the micro SD card as 0000.wav, 0001.wav, 0002.wav...

And play some music :)