barrel connector

A barrel connector is the cylindrical plug used to connect a power supply to a pedal's power input¹. On guitar pedals it is most commonly a 5.5mm x 2.1mm size, described as the standard connector that fits most modern pedals². Pedals specify the required connector size and tip polarity, such as 2.1mm with negative center¹, positive tip³, or negative tip⁴. Many pedals require a 9V DC supply with a center-negative 2.1mm barrel connector⁵, and some specify that the supply be isolated⁶. The 2.1 x 5.5mm center-negative barrel connector is the same as standard Boss connectors⁷.