AP OFC VS. OCC (Crystal)
Comparing the Analysis Plus OFC (Copper Oval-In Micro) cable versus the next-level-up Analysis Plus OCC (Crystal), there is an audible difference for sure. I have both types and compare both periodically. Both are nice cables and do sound quite different from one another.
AP Crystal OCC:
On my system, not only is the occ crystal version more open and wider as noted by @hilde45, these cables also have:
-more low end extension of BASS
-SMOOTHER sound, no edge or grain
-larger/wider SOUNDSTAGE (yes)
Woah:
The first time I tried a pair of the AP "Crystal" OCC cables it was so different for a split second I thought an input tube on one of my mono tube amps had gone microphonic or something. Switched back to OFC, nope. They OCC cable is just so much lager, wider, spatial. Kind of intimidating at first and they do need lots of settling in.
At first, It took a while to comprehend and appreciate the difference after having used all sorts of different OFC, pure copper, silver over copper cables from other top manufacturers. They pass-thru what is there from the source, good or bad. If you want a veiled over passive filter type interconnect or speaker cable, the AP "Crystal" OCC cables are not it. After getting use to the occ crystal cables ended up going back and swapping CAPs on my DAC and re-rolling a bunch of different input tubes on my preamplifier and amplifiers, now hearing input tube changes more than ever with AP OCC Crystal cables. Would have not believed it myself until I finally demoed a few pairs and bought some.