This is a comparison between opamps (LM308 and OP07) for those on the cusp of deciding which sounds better in the Rodent offered by
http://www.generalguitargadgets.com/ . The original ProCo Rat (tm) came with a 308 leaving many to suggest the original sounded better.
Technical notes:
The circuit in the two pedals is identical. So, too, are the pots used for volume, filter, and gain. I even took great pains as closely match the length of wiring within the box when wiring up the Rodent with the 308 (for the scrutinous ones).
Each pedal has a Duracell battery taken from a brand-new double pack and placed in the pedals at the same time. The voltages on the batteries read identical.