Not to be an ass, but in this case I reaally dont see how different cables help. Its a USB cable, meaning its carrying a digital signal, a bunch of 1s and 0s.
1s and 0s are 1s and 0s no matter what the cable is. Unless the cable is so bad and theres so much interference somewhere that the signal itself gets corrupt, but at that point it just doesnt work.
Thats the wonderful thing about digital. It works or it doesnt.
Check out what happened when broadcast TV switched to digital. No more noise issues and comparing different antennas. The channel either worked or it didnt.
The only effect here is, maybe, the better cables carry the power over USB better. But its such a small current, and its been stated that the Modi filters the USB power input anyway.
So I dont know :\ ...
On another note, I do like shiny cables anyway:
DIY 4 Strand Braid of solid silver.
Well, that's fine with me. I didn't think it would make a difference either. I bought the cable direct from Tellurium Q on the 30 days return thing and seriously I told them that I will most likely be sending it back cos I did't believe in this crap. Made a believer out of me.
If you're willing to investigate, I think there are many places that offer a no-questions-asked return on cables. Start with about 100USD budget and see if it makes a difference or not. Try something like a WireWorld cable or Pangea something that isn't obviously just another free cable dressed up. If you notice a difference, another avenue of system tweaking opens up for you, if you don't then you can send it back and never have to worry about USB cables ever again and leave idiots like me to it.
On another note, I'm here listening to the Modi from my MacBook Pro -> USB cable -> Modi -> (the tiny cable from BJC - MS1?) -> X-Cans V2 -> Grado SR225 and I've concluded that there's next to no difference between the BJC little cable and the AQ Evergreen (which came free with something I bought a while back). But the change between the UV7 and StraightWire is a quite a bit more pronounced than swapping the RCA's. Again the UV7 is thinner-sounding and the SW this time more mellow and more boomy and bassy the difference is fairly small, much less pronounced than with my Lehmann Linear last night but it's there.
Now, science says that the USB cable doesn't really carry whatever signal eventually translates to a bass note or a voice differently, but some cables do sound different to me while some don't. I tend to think it unfortunate since I have to spend money on usb cables but then again, some people buy designer clothes to make themselves feel better. Some feel that giving to charity gives them good karma and some believe in an afterlife. I happen to feel that USB cables make my dacs sound different. Which is perhaps just as reasonable seeing that I actually hear the difference.
Regarding the design of the USB interface being filtered, isolated, fortified with vitamins etc, I'm sure the Schiit team specially Mike Moffat, knows what they're doing and more. I'm sure no dac designer on earth is going to say "well, we sort of left it all crappy cos we couldn't be ar$ed". The same can be said for output and input stages both digital and analogue on all equipment - they're all designed as well as possible (for the designer) to a given budget/margin. But that doesn't stop interconnects doing things to the signal, does it. So why should USB cables all sound the same just because it's all filtered up and all that. Again, I believe in what I hear. Some don't hear the same as I do and that's fine with me.
Final note, I've paid for all these cables as I actually needed all of them in different places. I bought the UV for a bit of an investigation and since it was also at a good price. The Pyst I bought at the same time as the Modi and the Black Diamond I got cos I was impressed with the Black but needed a longer cable. I still have a fair few days left on two of them to send back if I want to so I'm not trying to justify spending my money on any of the three. Just wanted to share what I found.
p.s. It seems very strange to me that while it's so very easy to try different USB cables*, not many people do. I live in Thailand and it's bloody hard for me to get thing back and forth and still I can try them for like 2 weeks or something at a time. You guys in the US should do this more.
* - easier than RCA or XLR interconnects as there's little possibility of blowing things up or getting strange noises from your headphones.