Airplay to Bose Cinemate GS Series II

Hi there, 

I am streaming music via airplay from an iPhone to a Bose cinemate GS series II. I have this set up in two rooms but it’s slightly different and I am noticing a quality difference. I’m wondering if this some kind of placebo effect or there is a reason for the difference. 
Room 1 set up: AirPlay from phone to Apple TV (3rd gen) optical to Bose cinemate GS series II. 

Room 2 set up: Airplay from phone to Samsung TV (high end 2019 model) optical to Bose cinemate GS series II. 
I can notice better quality in Room 1. I am wondering if there is some kind of Audio loss, but logically there shouldn’t because it’s all digital right?

Would appreciate thoughts. If there is logical reason for the difference, I’ll buy another 3rd gen Apple TV for Room 2.
Are the TVs both set to PCM or another compatible setting?  Just guessing. 
Don’t have HDMI input audio. Am using airplay to the TV. I’ve checked the settings and can’t find the PCM setting. I’ve bought another Apple TV now anyway.