The iDefender 3.0 is an interesting product; it doesn’t filter any sort of noise via the differential signals of USB that can sometimes cause connection to fail but completely cut off the +5V and 0V from the host.
This effectively cut of noisy power supply and ground loop from the host at the start of transmission, only the +/- differential data lines are connected to the USB-DAC. If the USB-DAC requires a DC power to operate it can easily connected via the microUSB to a external low noise linear power adaptor.
My impression is better refinement in the highs via my i5 NUC running on ROCK to the Holo Spring DAC! It is cheap to try, any cheaper, you have prey on the USB cable!
http://majorhifi.com/ifi-idefender-3-0-review/
http://ifi-audio.com/portfolio-view/accessory-idefender3-0/