Jolida 302B audible hum

Hi, I can hear a relatively big hum from my speakers everytime my refrigerator (not far away from my system) starts. This had never been happened on my previous SS amplifier. Is this one of the natures of tube amplifier? Does it help to upgrade the Jolida power cord?
Thousands of thanks.
Are both on the same circuit? Do you have a dedicated line for your equipment?
Thanks Larry. I guess they are on the same circuit. I don't have a dedicated line for my systems.
First change either the fridge or the amp to a different circuit. If that doesn't work, try floating the ground - You'd just need one of those .99 cent cheater plugs that allow you to plug in a three-prong plug, while only having two prongs to plug into the outlet (having eliminated the grounding plug). Give that a shot before spending big bucks on an aftermarket cord.