The Technics SH-AC500D Digital Surround Processor can decode DD, PCM, DTS, or Stereo. It can take either coax or optical S/PDIF inputs. I am using a coax input and it is set to Stereo at the moment. It will also play fine with this input on Surround but not on DTS, which seems correct.
So again, a 44.1HKz digital coax s/pdif signal that plays fine fed to this Technics decoder will not play when fed to the 990.
Allen