I bought Onkyo Home Theater System HTS-570 (it has receiver TX-SR302) 3 months back. All was going well. But for last few weeks I am not getting any sound from center speaker. I tried swapping front speaker with center speaker, and the speaker works. So its to do with center channel on the receiver? Only other thing that might have changed is that I started using optical cable for my DVD player. But I do not remember if this started happening immediately after that or not. Is there a setting on the receiver that I might have changed by mistake, causing no output from center channel? Pls. help!