I think you will find that one 9 volt battery would not last any time at all. the 6 AAs have a big capacity and that's why they use them, a little 9v battery is intended for low power equipment. I see it is supplied with a 12v AC adaptor, if you connect a 12V battery via the adaptor socket you may get a longer run time if its a rechargable battery even better.
Answers & Comments
I think you will find that one 9 volt battery would not last any time at all. the 6 AAs have a big capacity and that's why they use them, a little 9v battery is intended for low power equipment.
I see it is supplied with a 12v AC adaptor, if you connect a 12V battery via the adaptor socket you may get a longer run time if its a rechargable battery even better.