OK finally got some testing to compare:
PC--> USB 2 cable (0.5M) --->isilencer ----> Regen USPCB -- DAC vs
PC--> USB 3 coupler x 2 --->isilencer ----> Regen USPCB -- DAC
USB cable -
https://silversonic.com/products/digital-cables/mirage-usb/
I got it for $160 sale (200) for 0.5 M, but now it is only available in 1 M . (why ???!!)
The final verdit is that USB cable got beaten by just 1 Chinese USB 3 Coupler
It was close battle but not that subtle if one listens very carefully.
There is definite more naturalness and analogue flow/smoothness to the USB 3 coupler.
The sound with the USB cable is a bit harsher/harder/more grainy, but has a bit more warmth.
The USB 3 coupler is slightly clearer/more transparent, esp on the piano tone, but a bit cooler (only by comparison) and more high tones, giving a fuller top notes but not the shrillness.
I think the USB cable has a bit of color (warmth) that has been noted before already.
How can a cheap adaptor beat a USB cable ? Of course it can I suppose, as it is so much shorter than the cable, as you know sound degrades with length so every cm counts. For electric USB signal the shorter the better.
This is nothing new, the Regen guys sell their adaptor for this very reason!
But the Corning USB is likely a different animal, as there is probably much less jitter as well as galvanic isolation, immune to EMF etc... and with optical, the length does not matter much like optical fibers for internet.
I would definitely try the Corning next very soon
But I am curious if I replace the USB coupler with another Regen USPCB would that help more ?
Thanks agaoin to 801evan for sharing his various non-hi-fi gadgets/products!
(note the USB cable for Hi-Fi is really a marketing ploy to try to get people to buy expensive cables so they can charge for shielding etc by making it longer than needed. etc... it is hard to find any cable 0.5M or less)