I am having a problem with optical sound from a DISH 622 DVR to a Yamaha amp. We first noticed it on ABC with good morning america. There is no sound except a low rumbling from the sub-woofer. When the source changes from the national feed to local, the sound returns. Then when GMA is over and the source changes to another national feed program, the sound also returns. This same thing happens on some of the national news. We've not noticed it on evening programming. But the problem isn't limited to ABC or local broadcasts. We enconter the same thing on some non-broadcast programming. The problem happens with some programming that has 5.1 sound and some with stereo only sound. I've used all the different settings on the amp and DVR but nothing corrects the problem. Regrettably, I don't have another amp. to test with. We do have a blu-ray player and have never had a problem with the optical sound on any source material. I switched out the optical cables from the DVR and blu-ray. The problem remained on the DVR so it isn't the cable. The DVR feeds into the TV using HDMI and the TV sound has always worked and still does. But the TV is stereo only. The TV has an optical out but the TV converts any digital sound to stereo so I can't determine whether the DVR or amp is the problem that way. Has anyone ever had this problem? Any suggestions as to how I can determine which unit is the problem? Any suggestions appreciated.