Peng is correct.
You have to turn HDCD decoding Off in the Oppo if digitally connected to an AVR or Pre/Pro that also has HDCD decoding. I have had a few players with HDCD, and the Oppo 93 is the 1st one that I have seen with an on/off toggle in the menus. If you are using an analog connection, you will leave it on, but for digital with a downstream device doing the decoding, you have to turn it off.
Brian