USB as a power source

Would it be feasible to power the empeg with one or two USB ports? I've seen cell phone chargers and lights that work via USB, so I thought this might be possible?

Thanks!

Even the Karma draws too much amperage to be powered from USB, how do you expect the car player to do it?

(There's a limit in the USB specification.)

Each USB port is in theory capable of supplying 500mA at 5V as a max. If you have an unpowered hub on the port then that 500mA@5V will be shared amongst the hub devices minus whatever is needed to power the hub itself.

Firewire could probably power it but again, it depends on the port. It's in theory capable of supplying 40V at 1.5A.

I hacked my ipaq cradle to provide charging... If I let the battery drain completly then try to charge/sync, I get errors out the wazoo complaining about power surge (or something like that) on the usb port. I then have to unplug the hub and plug it back in (happens on the mobo usb ports too, I need to reboot to make them work after that) . I can't imagine trying to power a whole friggin empeg with it