Check your Oppo settings. The Oppo can output SACDs as a DSD stream which I don't believe the 975 supports. It should be a pretty quick fix if that is the problem.
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Emotiva XMC-1, Outlaw 7500, Sonus Faber Olympica III Fronts, SF Liuto Center, SF Surrounds, LFM-1 EX, Oppo BDP-103D, Apple TV (Gen. 4), Mitsubishi 65" Diamond DLP, Outlaw Cables, PS Audio Power Quintet, Duet and power cords.