I made a one-knob treble booster myself. Since it's not a clean booster, it will distort when you turn up the volume. ・Control: Volume ・Power: Center negative ・Case: 100-yen store container (JNR refrigerated container) Power supply and adapter are not included. It's a center-negative DC adapter. I try to make them carefully, but it's a handmade item made by an amateur hobbyist. I've made sure it works without problems, but there may be initial scratches on the case or minor scuffs from the manufacturing process. Please purchase if you understand that it is handmade. If you have any questions, please ask.