I have a cambridge audio 350 stereo amp connected to a cambridge 540R receiver. I have connected them as instructed in other posts, but I cannot get any 5.1 sound form the receiver when watching dvds. Only sound through the front left and right speakers. The reciever is indicating on the display that it is decoding 5.1. Stereo sound is fine while listening to cds on the dvd player.Can anyone help?