Only other thing I can think of is to check the Sony's settings to see if you are set to send audio through coaxial and not just HDMI.
McIntosh's headphone amp may be more suitable for your needs. It can play small bookshelf speakers as well should you need to expand its use later.
https://www.mcintoshlabs.com/products/headphone-amplifiers/MHA150
McIntosh's headphone amp may be more suitable for your needs. It can play small bookshelf speakers as well should you need to expand its use later.
https://www.mcintoshlabs.com/products/headphone-amplifiers/MHA150