How to get Right and Left Channels to work separately?? (Output Channel mode)

Hi all,

I can't get this working.
I already changed the "Output Channel Mode" to left and right on 2 players + I set synchronisation on both players.
But... it doesn't work! For the moment both channels play Right + Left together...

Potential issue => One player is a Squeezelite player (raspberry), another one is an Airplay device and the third one is a Chromecast...

Any advice for me?

What I want to do (when this test works) is to use 2 raspberry's with their own amplifier connected to 2 speakers (one as a server and the second one as a client) and get stereo.

Thanks!
brannou