http://godlyke.com/maxon-guitar-effects/maxon-nine-series-effects/super-tube-pro-plus
A salute to the rare and highly collectible "Super Tube Screamer" from the 1980's, the new Maxon Overdrive ST-9 Pro+ Super Tube takes the basic design elements of that coveted vintage model and brings them into the 21st century.
Loosely based on Maxon's classic "808" circuit, the ST-9 Pro+ Overdrive Pedal offers a dedicated midrange control that varies the amount of Midrange boost, creating powerful, fat and heavy distortion sounds akin to a full stack amplifier. A mode switch to select from two different diode types allows the user to fine-tune the ST-9 Pro+ for use with single coils or humbuckers, while switchable 9- or 18-volt operation provides increased dynamic headroom and fuller frequency response.
When you're ready to step beyond the standard overdrive, the ST-9 Pro+ Super Tube OD Pedal is the only choice for the discerning overdrive connoisseur.