Here we have a rare bird from the early-mid 70s. A tweaked version of the the circuit found in Freedam Preamp amp found its way into some Big Muff enclosures. Original is very pricey and rare.
The original ran on two 9v batteries for bipolar power supply for the op amp section but I added a bipolar voltage converter so you can use with your normal power supply. A Master control is added at the end of the circuit so you can crank the volume control to achieve overdrive at reasonable levels. Also, the trimpots value remains unknown but I would shot for 10k...
The facory schematic is avaiable HERE.
