USB cables

I am at a loss as to how could the USB cable make any difference in sync USB. In adaptive I see, the good old jitter, but in asynchronous mode? If the data transfer is accurate, and even the cheaper ones achieve this, what's left to be improved by the cable?
I'm not saying that there's no difference, for I haven't tried. I'm just looking for some technical explanation from the ones who know.

It only makes a difference if you think it will make a difference - even for adaptive USB. 99% (or more) "audiophiles" don't understand how their brain actually works nor do they understand how to really prove if they actually can hear a difference. There may be very minute differences in timing, but hearing any difference that *may* be caused is beyond what our ears and brains can accurately detect. Yes, this is heresy for this type of forum and many people would have less income if people were "more informed". Just because thousands of people believe something, doesn't mean it's true.

no conductor is perfect... unless its a super conductor at close to 0 degrees kelvin. So all of audio science for wires is really about eliminating conductor non linearities at room temperature. The hardest wave to reproduce on a metal conductor is a square wave yet thats exactly what a digital signal is. So yes a USB conductor thats flatter in impedance linearity across a wider frequency range will suffer less digital anomalies. The sad part about audio is that metal conductors for digital is a dead end... they can't handle the frequency extremes as well as optical cables with lasers. Audio needs to adapt the gigahertz technology used by telcom at which point there will no longer be a signal difference if your carrier wave has a jitter error less than 1/1000 %

Hello, I went from a .5 meter Wireworld Starlight usb cable to a 1.8 meter Furutech Formula 2. I just installed the Formula 2 and really really like it a lot! Everything got better sonically right out of the box (highs to lows), high end resolution and clarity, more bass weight and "meat on the bones." This usb cable immediately made the biggest positive improvement of any cable I've purchased. The Formula 2 is causing me to wonder how other Furutech cables measure up against the competition. And I'm a person who never gushes about cables, quite the opposite. I've more often than not been disappointed in the performance of many cable purchases I've made (speaker cables, interconnects and power cables included). This one bucks that trend. I can highly recommend the Furutech Formula 2. (Macbook Pro to Rega Dac)

How important for the sound quality is the USB cable when using a USB/SPDIF converter like Audiophileo or JK HiFace?

I think you should go with the best USB/SPDIF converter you can afford (V-Link -> Audiophileo 2 / JK SPDIF mk 3 -> HiFace Evo + Evo Clock + PSU) and only after that try different USB cables. IMO this brings greater improvement that replacing the USB cable.