Mesa Boogie Mark I / Mark IIA / Mark IIB / Mark IIC / Mark III / Bass 400 preset

Verified · 90/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

A schematic covering the full early Mark series lineage — Mark I through Mark III — plus the Bass 400. These amps defined Mesa Boogie's identity: the original boutique high-gain American sound, with cascaded gain stages and a tight, articulate response that influenced virtually every high-gain design that followed.

• Years produced: 1971–1990
• Made in: USA
• Wattage: 100W
• Channels: 2
• Preamp tubes: 5× 12AX7
• Power tubes: 4× 6L6

Known for: Carlos Santana, John Petrucci, James Hetfield.

Heard on: Master of Puppets — Metallica (1986).

Tags: american, high-gain, vintage, mark-series.

Schematic-derived preset files for 16 Fractal and Line 6 modelers: Axe-Fx II/XL/XL+, Axe-Fx III, FM3, FM9, and the full Helix family (Floor, LT, Rack, HX Stomp, HX Stomp XL, Native).

Gridleak extracts amp parameters from original circuit schematics using AI vision — component values, gain staging, tone stack topology, tube types — then generates native preset files for every supported modeler. Every extraction is scored 0–100 and the score is published.