You can replace the internal power supply but I am not sure if Denon would do it for you. An alternative is to use a step up transformer to step the voltage up from 120V to 230V but it will not convert the frequency from 50 Hz to 60 Hz.
Since the 230V European Denon 3806 is designed to work with Europe's 50 Hz power system, it can work with the 60 Hz power system in NA. The other way around is generally not desirable.
