Copio el test que hizo un usuarione CA:
Testing The Chromecast Audio
My Chromecast Audio is connected to an 802.11ac network on the 5GHz band. I'm using the stock 5V 1A power supply included with the unit. I am much less interested in its DAC capabilities, so I only tested the unit's digital to digital conversion via the 3.5 mm mini-TosLink output (cable not included). The all-important firmware version is 1.17a.49061.
My first test was to stream Spotify to see if the audio was no longer converted from 44.1 kHz to 48 kHz. This was a success. Spotify streams at the correct sample rate of 44.1 kHz. For those unfamiliar with how Spotify works as a cast-enabled application here is a quicker than quick explanation. The Spotify app on an Android or iOS device is used to select music for playback and to select the output device, in this case a Chromecast Audio. Upon selection of music for playback the music is streamed directly from Spotify's servers to the Chromecast Audio device. This is very different from Apple's AirPlay because AirPlay currently streams audio from Spotify to the iOS device then on to the audio playback device. AirPlay uses the iOS device to route music through it and requires the iOS device to be in a certain state to continue playback (and continues to eat battery life of the iOS device). Using Spotify with the Chromecast Audio, the user can even turn off the Android or iOS device once music is selected for playback. The Android or iOS device is simply a remote control. Just as your television doesn't stop playing video when you change batteries in your remote control, Spotify and the Chromecast Audio don't stop playing audio based on the state of the Android or iOS device.
Spotify = Success
I moved on to testing my local lossless library stored on a NAS. There are several ways to go about streaming local music to a Chromecast Audio device, as evidenced by the discussions in the forums and elsewhere online. I elected to use Plex media server because it offers what I consider to be the best design for what I believe is the most popular way to use a Chromecast Audio device. Plex can run on a NAS or a regular computer, it offers a remote control app and a host of other features. Don't get me wrong, the other ways of streaming a local collection or Qobuz streaming are great, but I focussed on Plex as I believe it's the best option for most people.
The first tests with local music identified a major issue with the Chromecast Audio. I tried basic 16/44.1 music and couldn't get anything to play. I searched forums for hours and tried several "fixes" to get it working but nothing resolved the issue. In my frustration I tried a higher resolution file and it played! Thus, I started looking at my files and discovered the Chromecast Audio doesn't work well with uncompressed FLAC files created with dBpoweramp and some additional dBpoweramp levels of compression. More on the issues below.
16/44.1 FLAC uncompressed bitrate 1412 ripped from CD with dBpoweramp wouldn't play
16/44.1 WAV bitrate 1411 converted from FLAC uncompressed with dBpoweramp plays bit perfect
16/44.1 FLAC Compression Level 0 bitrate 926 converted from FLAC uncompressed with dBpoweramp plays bit perfect
16 bit / 44.1 kHz = Success
24/88.2 WAV bitrate 4233 is resampled to 48 kHz by Chromecast Audio
24/88.2 WAV bitrate 4233 resampled from original WAV with JRiver is converted to 48 kHz by Chromecast Audio
24/88.2 FLAC uncompressed bitrate 4240 converted from original WAV with XLD plays bit perfect
24/88.2 FLAC Compression Level 0 bitrate 2760 converted from WAV with dBpoweramp wouldn't play
24/88.2 FLAC Compression Level 0 bitrate 2766 converted from WAV with JRiver plays bit perfect
24/88.2 FLAC Compression Level 1 bitrate 2748 converted from WAV with dBpoweramp wouldn't play
24 bit / 88.2 kHz = Success
24/96 WAV bitrate 4608 converted from FLAC uncompressed with dBpoweramp is resampled to 48 kHz by Chromecast Audio
24/96 WAV bitrate 4608 converted from FLAC uncompressed with JRiver is resampled to 48 kHz by Chromecast Audio
24/96 FLAC uncompressed bitrate 4609 converted with dBpoweramp wouldn't play
24/96 FLAC uncompressed bitrate 4615 converted from (non-playing) FLAC uncompressed with XLD plays bit perfect
24/96 WAV bitrate 4608 converted from FLAC uncompressed with XLD wouldn't play
24/96 FLAC Compression Level 0 bitrate 2754 converted from FLAC uncompressed with dBpoweramp wouldn't play
24/96 FLAC Compression Level 5 bitrate 2590 converted from FLAC uncompressed with dBpoweramp plays bit perfect
24/96 FLAC Compression Level 0 bitrate 2761 converted from FLAC uncompressed with JRiver plays bit perfect
24 bit / 96 kHz = Success
Google hasn't announced support for sample rates higher than 24/96, but I wanted to test higher rates while I was at it, just to see if they would play. In my testing 24/176.4 and 24/192 wouldn't play and caused the Chromecast Audio to stop working with Plex until it was reselected as the output device.