Hotone Ravo MP10 Multi-Effects Guitar Processor with Audio Interface 8 Effect Modules , 130 Effect Types 100 Preset Patches , 100 User Patches AAA battery (x4) power supply and USB bus power supply available Make sure the Adapter is plugged in correctly. When using USB bus power, confirm the USB cable is connected correctly. When using batteries, make sure that they are still charged and the INPUT jack is plugged in with the cable.