Marshall JMP-1 - Clean preset

Verified · 86/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The JMP-1 is a 1U rackmount MIDI valve preamp with two channels, Clean and OD, each offering two voicings (Clean 1/2, OD 1/2) stored in programmable memory. Two ECC83s provide the valve gain stages, with diode clipping on the OD side, solid-state switching and EQ, a speaker-emulated output and an effects loop. It was a common front end for 1990s rack rigs paired with a separate power amp.

• Made in: UK
• Channels: 2
• Preamp tubes: 2× ECC83

Known for: Billy Gibbons, Billy Corgan.

Heard on: Bullet With Butterfly Wings — The Smashing Pumpkins (1995).

Tags: british, preamp, high-gain, clean, two-channel.

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.