Hi @abdo123, the AirPlay protocol uses the Apple Lossless codec (ALAC) at 16-bits and 44.1KHz. And the other components of balenaSound handle the audio data either uncompressed or as FLAC, also at 44.1/16. As long as your source media is 44.1/16, it won’t be converted and the chain will be nearly lossless. The main point of loss in the balenaSound system is in the snapcast multi-room portion, which has to adjust playback speeds to account for time issues on the network. But it is sending the audio data as FLAC.
Bluetooth audio may use a lossy data format between the phone and RPi.
Not sure about UPnP.
Pretty sure Spotify uses a lossy codec, since its streams are usually specified with a bitrate, e.g. 320Kbps. But I haven’t read up on the protocol yet, to know whether it has a lossless option.
I use a Raspberry Pi Zero W connected to my receiver via HDMI, and the audio there is very clean. The 3.5mm audio output on RPi is known to be low-quality. Pretty much any decent DAC will give you much better output.