Boss SD-1 Super Overdrive Guitar Effects PedalSince its release in 1981, the workhorse SD 1 Super Overdrive has been the core gain pedal for generations of players across every musical genre. Based around the revolutionary asymmetrical clipping circuit from the OD 1 Overdriveone of the three original BOSS compact pedals from 1977the SD 1 delivers rich, smooth, and highly musical overdrive tones that continue to inspire guitarists everywhere. Genre defining BOSS overdrive sound Unique asymmetrical