I'm having problems with getting DTS 5.1 to work. The NAD receiver does not have a built-in DTS-decoder, so I bought a Cambridge Audio Azur 540D which does and have connected the NAD and DVD player with 6 RCA cables. When I play DTS DVDs there is only sound coming from the two front speakers and the subwoofer. I select Ext 5.1 on the NAD and DTS 5.1 in the DVD titles menu, but it's no good, there is absolutely no sound from the center and rear speakers. Any input would be greatly appreciated.