I've only seen this crackling usually right after windows boots, on the very first sound test. Then on the next test it's as good as ever.
I think I may have heard it once recently after a reboot, maybe after changing a profile (on my phone?).
There's also a bug sometimes when you have the system "AC powered off" (hard power off, not just power switch) and then you boot windows with the X-fi plugged in and the sound channels don't work appear in windows and the device is locked at 16 bit 44 khz with no option to change it. Fixed by just unplugging and replugging in the USB.
The only time I remember this static issue never going away was on an old version of windows 10, which didn't allow higher than 16 bit/48000 khz with the Amp (but which had no sound quality issues with the Sennheiser GSX-1000). I remember something (maybe in this thread?) about some DLL or USB driver for sound being too old for the amp. V1903 fixed that but there was apparently a way to update even 1709 with that driver.
And make sure your sound is on 96000hz, 24 bit.
There is an "Issue" I've encountered twice (since the Amp was released) where it "forgets" or is unable to use 7.1 or 5.1 mode even when you select it in windows, none of the speaker channels will play sound except front left and front right.
The only way to fix that is to reset the firmware to default (I used my phone to do that), then to download your SXFI profile again.