Ok, thought so.
Well, i believe coaxial cable is better than optical but, optical is next for me. I didn't know if you had a hdmi output or not and thought you would have, so didn't suggest other solutions.
I'm pretty sure if you've got a Optical slot on the tv, it will be output, cause it would be stupid to be input.
So buy a optical cable and plug it in there and then into the receiver. You may need to change your sound source, i'm not sure how hitec your receiver is, you may need to change the digital input to optical.
The hdmi is video and sound as i said aswell , but can also be set to send only sound/video, same as a PS3. You can make it send video and let optical cable run your sound.
Well, to conclude it all up.
Get the optical cable, run it into the receiver and it should work.