I've buyed a Sony STR-DB790 Amplifier amb I'm impressed with it. I have it connected to a Sony DVP-NS355 DVD player and it sounds nice with CD-Audio or MP3 discs. Now I've tryed a DVD movie but the amp doesn't detect the multichannel signal and only does stereo. The disc is Dolby Digital EX enconded and the player shows the DD sign on the display. But the Amp doesn't make multichannes output. I've selected the A.D.F. Auto as indicated in the manual. But doesn't work. Anyone has this problem? I'm doing something wrong?