I know that there are small USB Isolator modules available, for example from Phidgets, but also via eBay. This is the Phidgets one:
Phidgets state: "The USB Isolator is designed to protect your PC from harmful voltage that can flow from devices attached to your PC through the USB cable. The isolator is inserted between the Phidgets board and your PC.
The USB Isolator can also be used to eliminate problems caused by ground “voltage” differences between USB Host and USB devices."
The eBay seller further states that "Isolators can be useful in low noise audio environments to eliminate ground loops."
It seems logical to use such a device between the (presumably) noisy USB bus of the host music server PC, and the DAC or, in my case, the HiFace Evo asynchronous USB converter, in order to minimise any negative effect of the PC. Is it logical to assume such a thing? If anyone can explain how these isolators work, particularly with an eye on audio applications, I'd be very grateful.