I bought a few days ago the Playbar and tried to connect it to my amplifier Onkyo TX-SR508 via the optical cable.
I use the amplifier because in hdmi input I connect the firestick / Sky, PS4 and hdmi output I have a video projector.
The problem is that audio through the optical cable does not work with the playbar.
Best answer by melvimbe
The device I listed above could perhaps replace your receiver entirely since it can switch between 3 HDMI inputs to HDMI out (for projector) and optical (for playbar)