I'm not sure if the newer Samsung TVs are similar to my current older one but I had to go into the settings on the TV itself and tell it to use just the external speakers instead of the built-in ones. Never tried with a TOSLINK connection (optical) but it may work the same.
If you find a post useful, please give the author a "Kudo" or mark as an accepted solution if it solves your trouble. 🙂
