DoP support for DSD512 would require a DAC with a PCM sample rate of 1411.2 kHz. You have to use ASIO for that one, not WASAPI, and make sure native DSD is being used and not DoP in the ASIO driver's device settings in MC's Options > Audio > Audio Device section. But it sounds like Matt has this DAC too, and it doesn't work for him with ASIO with Media Center it looks like you should contact Fiio, like Matt also said, and see what they have to say (since it's their driver seemingly not working with Media Center).