I'm using a Fiio M3 Pro's USB output into a Helix DSP.3 with the USB HEC card. I like the sound quality improvement over the Fiio's analog output, however the HEC card can't supply power over the USB connection. To make matters worse, the USB output seems to munch battery life faster than the analog out.
I figured it wouldn't hurt to ask, does anyone know of a way to simultaneously power a Fiio while using it with the USB HEC card?