Marshall JTM45 First preset

Verified · 88/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The JTM45 is where it all began — Marshall's very first amplifier, built in 1962 by Ken Bran and Dudley Craven under Jim Marshall's direction, loosely inspired by the Fender Bassman circuit but voiced for British sensibilities and an all-important closed-back cabinet. It delivers a warm, musical breakup with a richness and sag that remains deeply coveted today, sitting right at the intersection of clean and overdriven in a way that feels entirely alive. Its place in history was cemented when Eric Clapton famously cranked a JTM45 combo to record the Bluesbreakers' 'Beano' album.

Known for: Eric Clapton, Eric Burdon, Jimi Hendrix, Jeff Beck, Peter Green.

Heard on: All Your Love — John Mayall's Bluesbreakers (1966); Have You Heard — John Mayall's Bluesbreakers (1966).

Tags: british, vintage, blues, crunch, plexi, classic-rock.

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.