The Doom allows you to automate or manually control the crossfade between two input signals. The output is a mono combination that can be derived from two fuzz pedals, multiple pedal chains or even separate instruments being played simultaneously. Both the audio input and I/O are TRS jacks for optional dual configurations. An effects loop can be created that is split from the main channel, sent from the I/O, and received back via the second channel. Because the I/O is acting as a send, the return is via the ring of the input jack. By default the I/O is configured as the secondary input.