you know tbg, i had read about that potential before i bought them so i made sure that i bought the first "metal screen" and it seems to do the trick. no hums anywhere (i don't use tubes, for what that's worth), except when used on a cable box and, in fact, it probably exhibits less hum there than any of my other digital cables. i went with glass optical for that anyway, though.
this is from the vdh website:
>>The major difference between the members of our The FIRST ® series is their shield series resistance; Our The FIRST ®, The FIRST ® Ultimate and The FIRST ® Metal Screen progressively exhibit a lower shield resistance. (Respectively: ~14, ~4.8 and 0.0049 Ohm/m.).
[...] The FIRST ® Metal Screen with its lowest shield resistance has been specially designed for those situations where excessive ground currents flowing through the cable shield are present (e.g. with some tube equipment), in complex grounding situations and/or where extra shielding against strong external electrical interference is required (e.g. in highly electrical noise polluted areas). <<