Operational amplifiers allowed for the creation of distortion pedals in the early 70s by starting with a clean boost circuit.
Unlike the fuzz pedals of the 60s that overloaded transistors, these distortion pedals used op-amps to amplify the guitar signal cleanly before passing it through diodes.
These diodes then clip the loud, clean signal, allowing for unique sound customization and creating the distinct distortion that became a staple in music. This approach offers more control and versatility in shaping the distortion compared to the earlier fuzz pedals.