The thread did expand out significantly from the OP's comment about USB cables, to incorporate a wide variety of audiophile mythology.
Well, let's go back to the 'mythology' of USB cables and DAC sound quality then if you wish?
Here is a comment from an electrical engineer.
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"I plan to cover this more in the next article. There is some measurable improvement from using a USB cable with a ferrite "choke" at the DAC end of the cable. If you don't have a cable that has one, you can buy such a cable for a few bucks or get clamp-on ferrites in the appropriate size from electronics suppliers for a few dollars.
With any USB audio device it never hurts to use a USB port with either nothing else sharing that USB controller (cluster of ports) or only something benign like a mouse. High bandwidth devices like USB WiFi adapters, Bluetooth adapters, video hardware, etc. create more bus contention. While I haven't heard or seen any problems with the DAC on shared controllers (in fact I have routinely shared a controller with the dScope which generates lots of traffic) it's still not a bad idea with any USB audio device.
If your PC has front and rear panel USB connections, try to split any high bandwidth hardware between the two sets. Likewise some laptops have two groups of USB connections. As for other variations, the DAC's extra power filtering helps make it more immune to noise issues which can vary from PC to PC."