I just got my X5 from a local retail store (got lucky to get the last in stock unit). Sounds really really good.
However, I'm experiencing issues with the USB DAC function. The firmware is 1.2 right out from the box. I use windows 8.1 and had problem installing the driver. Googled a little bit and found fixes from fiio and now have successfully installed the driver.
My x5 shows the USB DAC screen when I plug it in the computer but it plays no sound. I have set the default playback device as the X5 but still no luck.
Any help would be greatly appreciated!