Yamaha Surround Sound and Arc

Hi,

I've recently brought a new Yamaha Home Cinema Amp and I am having a few problems. I have connected my TV via arc and also my technomate and Panasonic blu ray. I'm getting surround sound for both of those devices fine, but if I stick a USB in the TV and then watch media via that, I only get sound coming out of the TV rather than the amp.

I would have thought all sound would come out through the amp as I am connected via HD Cable and Arc, but its as if only the other devices (Blu Ray, Techno mate) are being picked up.

Has anyone got any ideas? I watch quite a lot of stuff via my USB and really want to get the amp broadcasting the sound.

Any help would be gratefully received.

Cheers