Is my power chord going bad?

Hello all, 

I have a power cord purchased from an independent cable maker. When I touch the interconnects running from my phono pre to my preamp to the power chord I get an audible hum coming from the speakers. This doesn't happen when I touch the interconnects to any other power chord in my system. The cord runs directly from the wall socket to my amplifier. 

Shouldn't a properly shielded cable not allow this to happen? 

Thanks for any advice!