As I understand it, HDCD is a VERY clever way to provide a few additional bits of information from a 16 bit media. If we only had 16 bit media HDCD would be a winner. However, the world has moved on to 24 bit media, and that changes the picture.
Some say that the 24 bit DVDA is not audibly superior to 16 bit CDs, so there should be no surprise that HDCD does not sound dramatically better. I have at least one regular CD which has the same reissued music as is on a HDCD. Frankly, the regular CD is better, probably because of the way it was mastered. The only CDs that light up the HDCD indicator of my equipment are ones that are so labeled on the case.
Some say that the 24 bit DVDA is not audibly superior to 16 bit CDs, so there should be no surprise that HDCD does not sound dramatically better. I have at least one regular CD which has the same reissued music as is on a HDCD. Frankly, the regular CD is better, probably because of the way it was mastered. The only CDs that light up the HDCD indicator of my equipment are ones that are so labeled on the case.