There are claims that sound quality improves by having a full galvanic isolation between the PC and the DAC. Some manufacturers of USB DACs use opto-couplers to eliminate the noise from the USB connection.

Isolated USB 2.0 with build in powertransfer EUR 36,11

The Adnaco-R1USB30 is a remote standard-USB 3.0 host controller which can operate at distances up to 100 m and more (depending on transceivers and cable) from the location of your computer. Powered by Adnaco PCIe over-fiber-optic technology, the R1USB30 was designed to suit many applications with the USB host interface. The R1USB30 provides 2 USB Root Hub Ports compliant with the USB 3.0 specification. All USB ports can handle the following interfaces:
• Super-Speed (5.0 Gb/s)
• High-Speed (480 Mbps)
• Full-Speed (12 Mbps)
• Low-Speed (1.5 Mbps)
The R1USB30 is connected to a host computer, equipped with the Adnaco-H1A card and a fiber optic cable. SuperSpeed USB is backward compatible with USB 2.0 devices and capable of operating with USB 2.0 platforms. The R1USB30 works with all USB systems and peripherals and does not require any additional software.

The USB Ranger® 2204 is a four port USB 2.0 high speed extension solution, enabling USB 2.0 connections at up to 480Mbps over multimode fiber optics.
Digital isolator simplifies USB isolation - Mark Cantrell, Analog Devices