Hi @gdaroch
Thanks for trying.
I gather your friend has no issues with his Beam at home? That would imply the issue lies elsewhere.
Do you have any other devices connected to your TV? If so, do you get the same issue with them connected? I discounted a possible HDMI-CEC conflict earlier as PCs don’t utilise it, but if another device is randomly sending signals to your TV when you are viewing the PC feed, it could conceivably cause problems.
It may also be worth changing Passthrough mode to Auto on your TV - after a recent update, my Hisense TV’s passthrough behaviour changed such that I had better results on Auto afterwards.
If you’re looking to connect your Beam directly to your PC, yes, you would need a sound card with optical output. Your TV should have this output socket already, however, and there’s a fair chance that optical will be more reliable than HDMI, though you are correct - Atmos will not be an option.
Finally, it may help to turn eARC mode off in the TV’s settings - ARC can handle Atmos via Dolby Digital +, which will “fit” on HDMI-ARC, and will work with streaming sources. If using BluRays, however, you’ll likely need eARC for Atmos.
I hope this helps.