Then it is probably induced motor hum (magnetic field) being picked up by the ultra fine guage cartridge wires and cartridge magnets (assuming you have a MM cartridge). New interconnects or shielding interconnects will not solve this problem. I suggest to try installing a ground wire from your turntable chassis to the preamp phono ground screw. If that doesn't work, try and find a part of the tone arm under neath the pivot (inside) that can also be tied to the chassis ground. To test the hum, simply shut off the table and see if the hum goes away. Power on..hum, power off...no hum. This will at least prove motor hum.
Wayner