Change the Power Voltage

I was following a discussion of an ad concerning a Gryphon amplifier that caused quite a stir among many,a few days ago. Part of the discussion touched on the power voltage of the amp at around 230-240v. It cited ,though ambiguously, that it can be change to 110-120v, so it can be used here in the US. 
I would like to know where can this be done. Change the power voltage. An electronics shop or dealer? Can anyone point me to the right direction? Is it possible to have a universal power selector installed instead? Is power voltage the only thing that needs to be changed and everything works well after it's done? How much does it cost? Estimates are welcome.
I am the second owner of a well cared Gryphon Callisto 2200 integrated amplifier. I tested the unit at our garage that carried a 240v line, it works.
I would like to thank everyone for any help that they can share.  Again, thank you.