SB Live! 5.1 Player to Yamaha RX-V659

Hello.
I want to put a computer near my TV and connect it to my home-theatre,
for playing anything is playable from PC: windows sounds, mp3, avi,
CD and DVD, games, etc.

I have an hold Sound Blaster Live! 5.1 Player and a new amplifier
Yamaha RX-V659.

I have thought to use the SP/DIF out of the SB, so I buy a cable with
a jack mono male and a RCA male. I have connected the cable but I
can't ear anything. I have modified any impostation of the control
panel of the SB; in the display of Yamaha I can see the label "DTS"
but when I play a mp3 or other the "DTS" disappear and re-appear when
the mp3 is finished.

Anyone can tell me something about?

Thank you and sorry for my english.

Bye
Fodox