You're welcome.
No, it is the other way around--you only need a regular USB cable to connect to the back of the K5, which would send USB audio signals into the K5. This signal is forwarded to the X7 through the dock, (or X3II / X5II / E17K) for the docked device to decode. The resulting analog signal is sent back out from the docked device into the K5 through the extra pins in the 11pin "micro USB" dock back to the K5 for amplification. Thus if you use a regular USB interconnect / extension cable here you'd get no sound out of the K5.
I am quite sure of this because I was working for FiiO when the K5 was launched and translated its manual and promotional material.
While we're at it--make sure not to connect the USB cable from the computer / smartphone / HiFi / whatever to the micro USB "Dock In" port at the back instead of the large USB In port next to it. As explained above the dock port (of which there are two, one at the top, one at the back, only difference is one is male, one is female) is designed to forward, i.e. output USB digital audio signals to e.g. the X7. The K5 is liable to go kaput if you feed a USB digital audio signal *into* the dock port at the back. There may or may not be a warning sticker about this on said micro USB Dock In port at the back.