Volume from different sources

Dear friends,
I got somewhat a problem according to Toslink input.
I am using RS201E; output is fixed to 2000mV, preamp turned off, amplification turned off as well. It is pretty much Roon endpoint or Tidal Client.
What is bothering me is that Tosling input has too low volume.

Would you please advise how to solve this issue?

I really appreciate any help you can provide.
Danijel

Hello, what device did you connect to the OPT IN of RS201?

Can you tell me if you have tested different devices and if they all did?

It is Leak CDT Transport. To be honest, I did not. Will do today and let you know what I found out.