Just fixed my SM7b noise issue be exchanging the XLR cable before the pre with a more expensive "pro" labeled cable. I guess the standard Thomann snake XLR arnt proberly shielded and before the pre any noise induced will be amplified along with the audio. It removed my noise problem which where fullspectrum whitenoise and slightly audible in recordings when going above 60dB gain on my GA Pre-73 DLX (also there with my fethead on lower gain settings). Now im considering what to do with the rest of my cheap XLRs, sigh...
NO cables produce 'hiss' on their own. If changing a cable really does alter the 'hiss' then in reality something else is going on, either the shielding is a bit suspect, in which case moving the route of the cable away from a source of RF interference may 'solve' it, or the original cable is wired incorrectly.
All cables are simply bits of copper or other conductor inside some insulation, nothing magic here, and they simply do not 'create' hiss, in the same way that a brick placed on the floor does not jump up and down of it's own accord.