^^ The USBpre2 is only powered by EXTERNAL battery - through the USB jack. I'm not sure whether the OP wanted something that was self-contained and didn't require an external batt. If you're talking about pres that don't require an external battery, there is the SD MixPre, although from what I understand, it really needs external power to get enough run time. Of battery operated pres that get decent run times off of a single charge to an internal or off of 9v batts, the littlebox, Aerco MP-2, Oade 248 are the first that come to mind, with the littlebox being far cheaper.