The basic Rat mod of ours requires drilling the case. We add a switch to make the unit more of a tone buffet! This is a must-have for people that need their Rat to be much, much more of an overdrive, tube amp pedal! Rat pedals ship with a chip that is different from days gone by, we'll get you the classic rat sound and more. We found a stash of the correct ICs. These are fast becoming rare and we have the heavy duty LM308 Metal Can version.
Rat Mod page at Keeley 's website...