Shogo_Takeda,
Thank you for reaching out to Apple Support Communities.
Currently Apple does not have any Thunderbolt to Coaxial or Optical Adapters. You can check with 3rd party adapters to see if they might work. Another option would be to see what other types of connections you can make with your AMP.
Here are the requirements to utilize Lossless.
How to listen to lossless on your Mac
What you need
You can listen to lossless on a Mac updated to the latest version of macOS using:
- A wired connection to headphones, receivers, or powered speakers
- The built-in speakers
- 14-inch MacBook Pro and 16-inch MacBook Pro support native playback of songs at sample rates up to 96 kHz.
- To listen to songs at sample rates higher than 48 kHz on other Mac computers, you need an external digital-to-analog converter.
More information can be found here: About lossless audio in Apple Music
Good Luck!