Upgrading a classic overdrive. The Boss SD-1W Waza Craft Custom Super Overdrive Pedal takes on the mammoth task of attempting to refine and improve the near-perfect original SD-1 design. The original SD-1 has earned its legendary status based on 40 years of peerless performance thanks to one clever feature- asymmetric clipping. Most overdrive pedals clip symmetrically giving a slightly thinner sound, that's because asymmetrical clipping creates more harmonic overtones. This gives a richer, thicker sound, overall. This design feature is patented by Boss (Roland) meaning the SD-1s are the only overdrive pedal that can offer this incredible tonal secret.