If you think you've already got some heavy tone, you should try this. Big Opiate is based on the superclassic Univox Superfuzz and has the same gnarly attack and powerful sustain with ringing overtones. It's tone shaping section, though, is tuned for way more aggressive sound that meets FZ-2-devotees expectations of massive wall of sound. This is an octave fuzz circuit and it's analog upper-octave presence is not as pronounced and sweet as in Foxx Tone Machine style pedals (like my Prophet), so it works perfect for a ripping, sludgy tones.
Fuzz circuit is followed by a mosfet power boost stage for huge output volume to smash your amp savagely and provide some additional tone saturation for extra filth content. So level knob is actually a boost control - when set to zero it doesn't cut off the effect like a volume knob, when maxed it will set any amp into heavy saturation.
fuzz - sets amount of sustain/fuzz
v (volume) - provides big amount of MOSFET-driven boost. CW turn reduces top end sparkle for even fatter sound at high volume level
scoop - blends two voicing modes: CW for maximum mid-scooped tone with massive low-end and aggressive highs, CCW for piercing high-midrange bite with smoothed highs and tighter low-end