Conrad Johnson Premium 12 noises

Need help on this one. I rewired power supply of Conrad Johnson from 110v to 220v as I am assigned to an overseas location, which is according to instructions from CJ and started to notice a continuing low but notable noise after connecting the speakers to the amp for both channels. Anybody has similar experience? Anybody know possible causes?
Thank you for your information, Thorman.
I connect another solid state amp to the same power outlet and there is no such hum sound not sure why.
Jeq : Sounds like a transformer hum to me..May have to live with it..Unless its really annoying..Check to see if the loudness of the hum changes at all..Somedays worse than others.Somedays barely hear it at all...kind of typical of transformer hum from crapy power coming in..Just my guess....I am by no means an expert...Good luck.....
Thank you for your info. Maybe I shall try to get a conditioner to see if it make things better.