Well....I think trying to convince Rio to manufacture and sell for a decent price a car adapter for the Karma is more or less a lost cause, I'm resolved to making my own or finding some other way that's cheap. So, I have a few questions...

1st, for the absolute easiest way around this problem, would the Karma (and dock) run off of a 4.5V supply rated at 1A?
2nd, assuming that the first is a no, and 6V would probably be a no, too, how much power (in Amps) would a 5V 3A voltage regulator require? I Can find everything else on the datasheets except that...

Bit of a blast from the past, but maybe the mp3mobile site might be useful here... the Maxim MAX787 as used on the mp3mobile is ideal for this sort of thing. 5A maximum output, input to 40V.

Just stick a diode in the supply (you can get big negative transients in cars) and use the application circuit from the Maxim datasheet. It's all through hole and pretty hard to get wrong. Heat dissipation is mimimal, especially as the Karma is most likely to be drawing only about 1.5A even when charging.

The inductor should be rated for 2x the max current you're going to draw, so a 3A should be fine.

Hugo

saw that
US only :-(

I may be missing sometning here but why not just use a power inverter with the AC power cord that comes with the dock?

http://www.amazon.com/exec/obidos/tg/det...en&n=507846

Major overkill, to convert from 12 volt up to 120 volt just to convert it back down to 5 volt. Not to mention taking up all that space for something that could (if done right) take up very nearly zero space.

Are there not suitable digital camera car adapters? I can find some 5V ones by searching but none of them list the max current they can supply. The plug on the Karma is also used by digital cameras from what I remember?

I happen to like using a power inverter. I have one plug for the Karma and another for something else, like a cell. Works great for my needs. Thats just me though. Just a thought.

Ah. Didn't click that