OK, I have a quick question... Why do some "wall wart" power adapters (transformer from AC to DC) work with 110v/60hz and 220v/50hz.. but others do not? Don't they all have the same electronics inside, with the only difference being the output voltage and amperage? Don't they all use the same sort of AC to DC conversion that would work with both input voltages/frequencies? Is the only difference that some are marked to work with both, and others are not? In other words, am I safe to plug in my power adapter for my dvd into 220v/50hz even if it isn't marked for 220v/50hz? (I bought my dvd player in Canada, but just moved to France, and I didn't bring a power convertor because all my other adapters say they work with both voltages and I just assumed this one would work, too...) It DOES say that it is marked for 110v 50/60hz, which is kind of strange since we don't have 50hz in north america... so why would they indicate both frequencies but only one voltage? Thanks for any help.