A group III nitride semiconductor device and a group III nitride semiconductor wafer are provided. The adaptive power supply comprises a reference voltage circuit having a plurality of field effect transistors collectively configured to provide a variable reference voltage, with different ones of the field effect transistors being biased into different operating regions. The voltage feedback circuit includes first and second resistors. a metal foil, with an irradiated gamma radiation sensitive adhesive on one surface. A speaker is attached so that a sound generated at the front of the speaker attached to a cabinet is led to a plane such as a front panel of a device by a waveguide, and the opening surface of the waveguide is almost perpendicular to the plane.