The Green Currant tremolo is a very percussive and vibey tremolo based around the TDA5072A amplifier chip. It splits the signal into two paths that are out of phase. One side is static and the other is filtered and amplitide modulated, then both paths are summed together. This results in what sounds almost like a light vibrato/phaser'ish effect.
Changes to version 1.5 (circuitwise it's the same)