I use my DACMAGIC with a Cambridge Audio 550C CD Player. I bought the DACMAGIC to upgrade an old NAD 541 unit, ¡but the NAD died suddenly!
After some months using the DacMagic, I think that the differences that the DAC may produce are subtle (using it with a good transport), these are more noticeable with human voices, then a lesser degree with acoustic instruments (like piano, guitar, ...). Then, the differences are much less noticeable, almost imperceptible when compared to electric instruments (like the rock music in general).
What I hear, especifically better with the combination 550C/DACMAGIC is simply more detail, more textures, better definition and enhanced image, and even I fell a more airy sound. In contrast to the 550C alone, I hear a thud sound, as if the speakers were covered by a thin pastic.
I need to clarify something: the Cambridge 550C is an excellent CD player, most people could live with the 550C very happy without an external DAC. I thank that sound of the 550C is better than my old died NAD 541 (if my listening memory don't lie to me, due to the fact that I wast not able to compare both CD players)