BD390 audio question - HELP!!!

[umterps98]

I just hooked up my BD390 to my Sony STR-DE545 (pretty old receiver) via 5.1 analog connection. The video on the BD player is outstanding. However, I am having some audio issues. My old DVD player was connected by optical. My current TV-DVR-receiver connection is optical. What I am finding is that the analog 5.1 BD sound is much lower and a little bit muffled when compared to the optical connections. I even turned my receiver from the "5.1" selection to the "TV" selection and the audio sounds louder and richer on "TV", which is connected via optical. In order to get the sound on the 5.1 to be at a decent level, I have to turn the volume up pretty darn high, much higher than for TV... What is the problem here? What settings should I have everything on? Thanks for your help!