I have just set up the Yamaha DSP AX 620 amp with a Panasonic RV20 DVD player, connected by digital optical cable. Amp is DTS compatible, DVD is DTS compatible. Dolby Digital is working like a wet dream but I can't for the life of me get DTS sound coming out (e.g. using Gladiator DVD, and choosing DTS from the input mode at the front of the amp I get nothing). . Anyone with this amp had a similar problem?