Nordost Frey interconnect hum

I bought a pair of used Nordost Frey unbalanced interconnects here and i noticed they induce a hum through my speakers when my preamp is off or when the cables are only plugged into the power amp. The strange thing to me is that my Nordost Heimdall interconnects do not induce the hum under the same conditions nor do other shielded interconnects. They do the same thing on another system as well. I understand that both the Heimdall and Frey have the same 97% shielding and the only difference is 2 extra center conductors. I'm waiting for the seller to ask Nordost but i thought i would ask here if anyone can explain it.

Thanks for any advice.