In General
The DF-2 Super Feedbacker & Distortion Pedal from 1984 to 1994 is a distortion pedal with an integrated feedback function. It is related to the DS-1 Distortion Pedal from 1978. Until 1985, it was called Super Distortion & Feedbacker, which triggered a legal dispute with Dimarzio over a similar name.
Details
When the footswitch is held down, an oscillator follows the guitar signal to synthesize feedback. It also follows when continuing to play this note. The DF-2 is not particularly loud, as the distortion circuit consists of a hard-clipping operational amplifier with silicon diodes fed into an attenuating Big Muff tone stack. The distorted signal is quieter than the undistorted bypass signal.