I would like to power an MP3 player that uses a single 1.5 volt AAA battery with a 9 volt battery. I have been using AAA batteries that are rated at 1,100 mA. They only last about 2 hours. Rechargeables last even less. Is it feasable to build a simple circuit that would allow me to use a 9 volt battery to power this thing? It would seem a 9 volt battery would give me power for quite some time. Any help would be much appreciated.