Now WiiM Mini supports Amazon Music HD/UHD on WiiM Home app, please make sure the firmware version of your device is higher than (4.6.420352) and update your apps to the latest version.
WiiM Mini supports the bit perfect output such that your audio output will match the resolution of your input source. Even though the SPDIF output resolution is set to 24 bit/192 kHz, it won't up-sample the audio to the fixed resolution of 24 bit/192k Hz. Please check the sample rate and bit depth of the played music on your native Amazon Music App or WiiM Home app and see if it matches with the output from WiiM device.
Moreover, there are different quality tags on the WiiM App. The HD tag means the original content is in 16 bit/44.1k while the Ultra HD tag indicate the content is in the resolution 24 bit/44.1k or beyond. Please select the music with 24-bit, 96kHz or 192kHz to try.
1. Amazon Music HD with WiiM Home app
Please follow these steps below:
1. Open WiiM Home app
2. Go to Browse -> Amazon Music to sign in your account
3. Go to Settings in Amazon Music screen to turn on Amazon Music HD/UHD Beta.
2. Amazon Music HD with Amazon Music Casting
Please check the setting in your Amazon Music setting on the WiiM App by select Browse tab > Amazon Music > Settings > Amazon Music HD/UHD.