It's based on a pedal from the early 80's from Pearl ( as in the drum company ) it's the Pearl OD-05
The OD-05 has a standard feedback-diode clipping stage like a Tube Screamer, but the magic is what
comes in front of it: a parametric equalizer that allows either a cut or boost of up to 15dB in a range from
100 Hz to 4 KHz.
With this flexible preclipping EQ, you can get some incredible sounds out of it. You can crank the mids
for a cocked-wah sound, or tune the circuit to enhance the resonant peak of your specific guitar and
amp. You can even get a scooped-mids sound if that’s what you’re after, something that’s pretty rare in
an overdrive.