It's possible there is no audible difference with some headphones and the included cables 1 foot length. Not sure.
A good test would be to try to use a longer length (like 5 feet) and try many different headphones. A closed and very revealing headphone is best.
I wonder what would happen if you placed 10 Ferrite beads on a USB cable
Sorry, I'm easily amused..
Wait! No audible difference, requires volume matching and blind A/B test. All placebo!
EDIT: I just switched back between cables again and it's definitely very audible. Less so on my Magni and open headphones. On my DJ100 it makes everything seem more congested and warmer, like the lower mids are more forward and there is less treble. If anyone tests this, try it with any music that's warm and has a larger soundstage. I tried some Tony Bennett recordings and "Buena Vista Social club". Recordings that can often sound congested on a very warm headphone are best.
I bet a good headphone to test the differences would be the M50 or a bassier headphone that has slightly rolled off treble. Even the HD-650 might do the trick.
What it sounds like is what happens I connect my Headphone amps up to a MOV based surge protector, but even worse. Same symptoms almost.
EDIT 2: I just bypassed my USB hub (powered) and went directly to my computer. I switched between a 1' USB cable with ferrite core and a 1' USB cable with. It's stupid easy to tell the difference. This was with the DJ100 and Headroom Micro Amp and ODAC. Similar results with HD-650. I highly doubt there can be an audible difference between USB cables even without the ferrite core (I know the whole 1s and 0s thing).
Hey, maybe it's the gold plating degrading the sound!!!
Only kidding...
I think this has to be the most bizarre thing I've encountered in years.