Higher level phono sections like mm carts rather than low output mc carts are less sensitive to EM induced hum from nearby transformers, etc. Shielded cables and/or supplemental shielding around the low level amplification device(s) like a step up transformer helps. See my system listing here on agon for an example. Adding shielding around my phone step up amp allowed me to use my preferred unshielded IC in my case and eliminate significant audible hum.
are some phono stages more resistant to hum?
After a tonearm upgrade, which mostly involved "improved" shielded cable, it now hums with tube phono stage (upgraded AR PH3-SE)but no hum with backup ss device (DB Systems). It appears the hum originates with the new wiring, but why would one phono stage be impervious to the hum? Do phono stages have different grounding schemes, making them more compatible with certain tt/tonearm/wiring combos in unpredicable ways? Are ss phono pres less susceptible to hum? Have you ever changed phono pre to cure a hum incompatibility? I see from forums that tt hum problems are common and sometimes difficult to solve. Shouldn't a shielded cable be more immune to hum, not less?