Tbg: Yes, all-carbon cables can be more susceptible to hum (although it's of the induced environmental variety, not caused by a ground loop), and this is the result of the higher resistance of the shielding in combination with the run length and what gear it's connected to. For certain runs in my system I use carbon conductor cables with metal shielding instead of all-carbon.
Will: Resistance is less of a factor for interconnects (in normal length runs), more so for speaker cables and of course power cords.
Will: Resistance is less of a factor for interconnects (in normal length runs), more so for speaker cables and of course power cords.