Marshall Jcm900 Dual Jmp52B Preamp Cd0189 Iss7 0349 preset

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

This schematic documents issue 7 of the JCM900 Dual Reverb preamp board (JMP52B, CD0189), capturing a mature revision of the two-channel preamp circuit used in the 4100 Dual Reverb. By issue 7 the preamp design had been refined through multiple revisions to improve channel separation, reduce switching noise, and optimize the gain staging in each channel. The Dual Reverb's preamp features two independent channels — clean/crunch and high gain — each with its own EQ controls, plus a spring reverb circuit that adds the characteristic Marshall reverb tail.

Tags: british, vintage, crunch.

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.