кто-то пользовался УСБ изоляторами, чтобы землю с компа убрать? на ибее можно за 35 баксов купить
ebay.com/itm/USB-protection-ADUM4160-Evaluation-Board-USB-Isolator-/230904140149?pt=LH_DefaultDomain_0&hash=item35c2f59175

Цитата:USB as standard interfaces to adapt to a variety of system platforms, and a variety of devices, the operation is very simple, and can to an external power supply. However, USB has deficiencies in the peripheral and the host must be a common ground can work. The host computer is usually more of a desktop computer. This case, USB is often the ground and chassis ground together, and this may be caused by the use of hidden dangers.

In addition, very often, need USB signal and the computer is isolated,

*When debugging for High-pressure board, if the design or operational errors, the debugger will burn out, or even the computer USB port;

*Some audio signal circuit, if the computer GND is not clean, there is clutter, it will interfere with the playback signal quality;

*Long USB cable for some applications, computer and target board GND GND pressure caused by ground loop exists.

The above situation, we need to do isolation of USB signal processing, to ensure system security and work.

ЦАП у меня с внешним питанием, вот думаю поможет ли такая приблуда?