Hmmm, The output voltage should always be 5v or very close as that's the usb standard. I'm not sure it's true to say the
only thing that matters is the output voltage though is it?
I notice that everyone here is using a BB chager about .5 or .7 amps to charge their HTC phones. HTC all seem to take up to 1 amp so that should work fine it might just take longer. I wonder though, what would happen if you plugged a 1 amp HTC charger into a BB that normally receives .5 amps from it's standard charger? Would it just draw the .5 amps or would it blow up?
That's the way round i'd like to try as I have loads of HTC chargers but only one BB charger.
PS. Point of interest. A usb data connection (charging from your computer) gives a maximum of .5 amps which is what most of these phones will draw from it when it is connected. I timed it (I was that interested) and it took nearly exactly half the time to charge my HTC with it's 1A charger than using a .5 amp data connection. I would expect you would find the same comparing charging times from a HTC 1 amp and BB .5 amp charger.
PPS. Wall sockets are 230 volts in Europe now.