Here is what Mike says...

'If you're on a mission to get your tone in sync and dialled in ...or maybe you're a mad scientist.. or perhaps you live in a post apocalyptic world where machines have taken over and you now live (and play guitar) in an abandoned military base).. then this is the practice amp for you. 

Featuring an internal speaker as well as output for external cab. Powered by internal 9v battery or standard 9v pedal power supply. It has controls for volume, tone, gain, boost and hi/low bass filter. Also on the panel are switches for on/off and internal/external speaker selection.'