The KOi overdrive is based on a popluar d-style overdrive but in a 1590A or 1590B sized enclosure with a few improvements. Has more gain, altered tone control and picks up less radio stations than the original but with the same tasty mosfet clipping and cool voice control. Demo vids Below, check 'em out. The larger 1590B sized enclosure has a battery or adapter power options while the 1590A is 9v adapter only (center negative 2.1mm).
Another great demo by Mr. Andrew Johnston.
Video by Curtis Kent at Kenttoneworks
Video by Guitar instructor extraordinaire Robert Renman.