Marshall Jtm45 Ri preset

Verified · 80/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The JTM45 was Marshall's first amplifier, introduced in 1963 and directly inspired by the Fender Bassman circuit. Fitted with KT66 output tubes and a plexi-style control panel, it became synonymous with the British blues-rock tone of the mid-1960s.

• Years produced: 1963–1966
• Made in: UK
• Wattage: 45W
• Channels: 2
• Preamp tubes: 3× ECC83
• Power tubes: 2× KT66

Known for: Eric Clapton, Peter Green, Mick Taylor.

Heard on: Hideaway — John Mayall & the Bluesbreakers (1966).

Tags: british, blues, vintage, plexi.

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.