The man behind the TwinStomp Booster, Adam Betts, did what many players feel forced to do when struggling to realise the tone they hear in their heads: he built a pedal himself.
Using a widely available design based around Mosfet circuitry, he simply constructed a stompbox and went from there. However, as a commercially available clean booster with two switchable settings proved difficult to find, he decided to incorporate that into his design and create something new. There is a swathe of technical info on the TwinStomp site if you'd like to really get to grips with the innards of the pedal.
The pedal offers two settings. Pedal two offers a maximum of 22.5dB of boost and is slightly hotter than pedal one - with each possessing its own level pot. There's an on/off switch and a blissfully simple-to-access battery compartment: just tug on the ring-pull and it pops out for easy replacement. It's true bypass too.
Sounds
Reference
Boost 1
Boost 2
The TwinStomp does its job very well indeed. Remember it's a boost, not a distortion or overdrive pedal, so it works best with all-valve amps to push them to (and beyond) that magical sweet spot of harmonics and drive. As everyone within about five miles will attest, it makes our hand-wired Marshall 1959 roar like a pride of lions when gazelle school kicks out for the afternoon. Moreover, it doesn't change your amp's core tone or EQ to any great extent.