Up for sale is a genuine vintage 1980 Electro-Harmonix Big Muff Pi Version 5 (V5). This is the sought-after late-70s/1980 "IC / Op-Amp" circuit with the rear Tone Bypass switch—famous for delivering the massive, saturated wall-of-sound fuzz heard on Siamese Dream.

Specs & Verification Details:

• Year: 1980 (verified by CTS potentiometer date codes: two pots coded 13780xx from 1980 and one pot coded 1377xxx from late-70s factory stock).
• Circuit: Original EH-3003 PCB featuring the dual 8-pin Op-Amp IC chips rather than transistors.
• Features: Rear Tone Bypass slide switch (removes the tone stack for a louder, punchier midrange boost), 1/8" (3.5mm) power jack, and no status LED as originally built.

• Fair Cosmetic Condition: Shows honest road wear, scratches, and patina consistent with a 46-year-old vintage pedal (see photos for exact cosmetic details).
• Functionality: Tested and working. Pots are a little scratchy, tone bypass switch was replaced.
• I've had this pedal since the 80's and was always in a non-smoking environment, with not a lot of road use, just studio time.