The Drunk Beaver Big Grunge is based on the Boss Power Driver PW-2 and is an iteration of Drunk Beaver's limited Pedal Drop Series "Mykolaiv Grunge", which is no longer available.
The key differences are that the Big Grunge uses pots, while the Mykolaiv Grunge used sliders, but sliders are harder to acquire according to Vitalii and so don't make sense in a regular pedal line. Using pots makes the Big Grunge a more giggable option, as the pots are much sturdier and there's no chance of spilling beer in the slider slots!
The Mykolaiv Grunge also had an EQ toggle to switch between stock PW-2 and custom EQ modes. The Big Grunge doesn't have this toggle but has a combination of stock and custom frequency bands which Vitalli has perfectly tuned straight out of the box.
The Boss PW-2
The Boss PW-2 was only made for 9 months in 1996 and 1997, and as such remains one of the company's rarest pedals - Vitalii has put in hours and hours painstakingly reproducing the original circuit design because so few accurate schematics exist.
The PW-2 was intended to be Boss's "grunge" pedal, but they were late to the party and obviously also overlooked the fact that Kurt Cobain was closely associated with the DS-1 (and the DS-2).
The PW-2 certainly didn't set the world alight at the time, but today you can even hear it referred to as the "Oasis pedal" - not because Noel ever used one, but because you can dial in a really awesome Definitely Maybe sound!
Big Grunge Circuit
The discrete op-amp design is typical of many Boss dirt pedals, but the biasing of the PW-2 is completely different and uses a lower voltage. There are also no clipping diodes - all the dirt is generated by overdriving the op-amp, which gives a really nice amp-like response.
The discrete op-amp FETs are Toshiba 2SK208 - the modern counterpart of what the PW-2 had - while the single IC used in the EQ section is an RC4558.
Big Grunge EQ
While the PW-2 had 2 frequency bands, the Big Grunge's gyrator-based 3-band EQ allows for finer control over your sound, and offers up to +-15dB of gain per band. The EQ is a combination of stock and custom modes on the Mykolaiv Grunge:
Low has the "custom" centre frequency of 80Hz instead of the standard 130Hz
Mid has the stock centre frequency of 890Hz
High (not present on the original PW-2) is set at a centre frequency of around 3.5kHz
As per the original, most of the EQ change is achieved in the last few degrees of each knob's travel, but despite this it's a surprisingly effective design - especially with Vitalii's tuned frequency bands.
Big Grunge Demo
Big Grunge Features
World exclusive - only available from Boost Guitar Pedals!
Upgraded and updated version of Boss PW-2, Boss's own "grunge" pedal.
Not a big fan of the graphics on the enclosure, but it's not how the pedal looks that counts, right?... this pedal is much more versatile than a PW-2. It sounds massive. Drunk Beaver is a fantastic builder & Boost is a top notch seller.