A DC wall adapter in the 7.5 volt to 9 volt range that can supply 650 milliamps or more is preferred. (I personally use a 7.5 volt 1 amp center positive wall adapter.) The synth requires a center-positive power supply, but it also has a rectifier diode, so if you accidentally plug in a center-negative power adapter, the synth will be protected from damage as a result of reverse polarity. Although the device's on-board voltage regulator can accept an input of up to 18 volts, a heat sink may be required to allow the voltage regulator to dissipate the excess heat produced at these higher input voltages. The power is supplied through a standard DC barrel jack adapter. The dimensions of this DC barrel jack can be found on this datasheet: http://www.mouser.com/ds/2/670/PJ-202A-524180.pdf
Please note that a DC power adapter is not included in any of the reward levels.