High-Speed HDMI cable (18Gbps or 48Gbps). Optical cables cannot carry Dolby Atmos.
You can listen to verify two things:
If you need help finding specific safe, legal test files , let me know your playback setup (e.g., PC, Nvidia Shield, Blu-ray player, TV USB), and I’ll point you to the right format and source. dolby atmos 71 4 test download link
Connect your PC, Laptop, or Media Player (e.g., Shield TV) directly to the HDMI input of your 7.1.4 AV Receiver (AVR). High-Speed HDMI cable (18Gbps or 48Gbps)