HDCD was a bit of an odd format. The process required the master to be HDCD encoded, and the audio to be HDCD decoded, upon playback. As mentioned, the Pacific Microsonics chipsets were the best, but they typically only appeared in expensive, high end gear. I had a Parasound DAC that could decode a HDCD disc, and while it didn't use the Pacific Microsonics DAC's, it still sounded very good. Also, concerning 'false positives'. A master needed HDCD encoding, but the PQ Subcode (the Table Of Contents / TOC of the CD) also had an area set aside for HDCD. There was an ON/OFF 'Flag' that needed to be set to ON, if HDCD encoding was present. I'd often receive master tapes, with no encoding, but the TOC HDCD Flag had been set to ON. So, on playback, the CD player would activate the HDCD display, and try and decode the audio, but there would be no audible benefits.