http://www.godlyke.com/hao-handbuilt-guitar-effects/rumble-mod - The ultimate overdrive unit, the HAO Rumble MOD RM-1 uses hand-selected components to provide the purest, smoothest, thickest overdrive ever. The problem with most OD's lies in mismatched input/output impedances that can make components work overtime. The Rumble's input and output buffers provide proper impedance matching, allowing its circuitry to focus purely on generating the fattest overdrive possible. The Rumble's two modes of operation -- Clean Boost in Mode #1 and Overdrive in Mode #2 -- allow for a variety of applications and tonal options. If you've been searching for that $10K amp sound but are several $K short of the mark, the HAO Rumble MOD is the economical answer to your tone quest.