Pedals that stack with the Dunlop MXR SUB Machine

JAM Pedals Retrovibe mk3

Keep Dunlop MXR SUB Machine's fuzzy voice out front: JAM Pedals Retrovibe mk3 goes after Dunlop MXR SUB Machine in the signal chain so its modulated voice doesn't muddy it

Walrus Audio Ages

Put Walrus Audio Ages in front and the fuzzy tone leans further toward clean boost

Fender Blender

Fender Blender stacks octave on top of the fuzzy already here

Pigtronix Echolution

Put Pigtronix Echolution after Dunlop MXR SUB Machine in the signal chain, clear of Dunlop MXR SUB Machine's own gain stage — goes in the amp's FX loop (or last, into a clean amp)

Walrus Audio Melee Wall of Noise Black

Keep Dunlop MXR SUB Machine's fuzzy voice out front: Walrus Audio Melee Wall of Noise Black goes after Dunlop MXR SUB Machine in the signal chain so its ambient voice doesn't muddy it — goes in the amp's FX loop (or last, into a clean amp)

W-LM Compression Fracture

W-LM Compression Fracture's own compressed character is the real reason this is worth trying