A long harsh digital trip - final meter?


So the digital signal manages to find its way to a utility pole in front of your house. Then enjoys a coaxial sprint to a modem, and then head over to a modem, router and then into a Roon nucleus. Up to this point, a rugged unprotected harsh trip. And now this signal flows along a very refined ubs cable and arrives at a dac for final prep work before reaching a high end system. 
      So why does the final leg of the signal’s journey inside a usb cable seem to matter so much toward improving sound quality? What happens here to revive a digital signal that has traveled hundreds of disgusting dirty miles to reach the analogue chamber of rebirth? So I guess it’s possible to truly transform and correct a digital signal during a very short journey thru a usb cable?
emergingsoul
My electronic engineer friend tells me that the various electronics and noisy switch mode power supplies in your home will inject noise into the signal, as well as all the components, from the modem onwards, that the signal passes through. Hence why a good quality network switch, linear power supplies, well-shielded Ethernet cable and well-designed usb can make a difference. 
I have tried various usb cables at many price levels and some make no difference to my system, whereas one my friend made himself, makes a big improvement.  As someone above said, the key to his USB cable is to not use the 5th wire in the cable, the one that delivers the power, as this is not required in self-powered DACs.
Do they sell usb cables without power wire?

cardas sells a $400 usb cable that separates the power wire, ie ‘high speed cable’
Good lord. Take a generic USB cable make sure it works, cover pin 1 which is the + with a small piece of electrical tape. Cut very small strip use tweezers cover only pin 1.  Compare to the $ 400 cable  to the covered pin cable and a regular cable get a friend to help do it without knowing which is which. 

Note. If your DAC can't cope with pin 1 it's garbage. 
Oh, great idea.   I’d prefer spending more money, but this seems more prudent. Now searching for audiophile grade electrical tape.
djones51, what you have suggested in terms of sound enhancement, I have no comment, as I have not done so. However, as to methodology, if you do not treat all the cables similarly, you are not showing superiority one cable over the other; you are showing a potentially efficacious method.

What if that method was applied to all the cables? Have you tried such a comparison?

BTW, have you actually done the comparison you suggest?