I've developed the exact clone of the famous DOD FX-32 Meatbox Subsynth pedal (original, not the reissue one). I was able to do that by having access to the original unit. My pedal is 1:1, 100% clone of the original Meatbox and it's true bypass. I'm using only the best components possible. Actually it's probably better than the original. Meatboss generates lower octave which can go down to about 20Hz. The pedal has 4 controls. 30Hz and 60Hz are bell/notch filters which are flat at 12:00. They add huge amount of sub frequencies when turned clockwise. Mix knob lets you set the amount of lower octave added to the dry signal. Volume also works exactly like in the original, but I've increased the maximum output 5 times, so it's way louder than the original.
Demo by Fritz's Guitars (EN)
Official Product Video (EN)