Power Conversion

I presently own a Classe CA400 power amp and the CP-60 preamp. Both units are set up for 230 Vac 50 Hz. I would like to convert these to US power 120 Vac 60hz. Does anyone out there have any idea what's involved? I was hoping it would just require changing the primary or seconday wiring on the main tranformer but maybe the complete tranformer needs replacing. Also amyone with diagrams or service manuals on these units would be helpful.