audio optical

I just purchased the LG BP620. I choose this because of the optical audio connection. My old DVD was connected to my Marantz receiver via an optical cable. I connected everything and the sound is aweful. i think I may have a defective unit....just wondering if anyone has experienced the same issue or better yet has successfully connected this unit to a reciever via it optical audio connection. Thanks.....

Thanks for the reply. The sound is "present" but out of sync and definately not loud enough. I had an older Panasonic DVD player hookup up the same way and the sound was great at the same volume levels.