A battery-powered wireless transmitter for connecting to a musical instrument comprising an antenna; a cover comprising a well at one end and a first gear on one side of the well; a T-shaped plug having a horizontal section pivotably disposed in the well and a vertical section projecting out of the well, the plug comprising a spring member at one end of the horizontal section, a second gear on the other end of the horizontal section being urged by the spring member to mesh with the first gear, and an electrically conductive rod projecting out of the vertical section; and an adapter comprising an end socket. Pivoting the rod about the horizontal section by rotating the second gear about the fixed first gear will adjust an angle of the plug with respect to the cover and fix the angle after stopping the pivoting.