Marshall JMP PA 1985 - Channel 2 preset

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

The Marshall 1985 is a 50-watt JMP-era valve PA head with two input channels, each with two inputs and its own volume, on the two halves of an ECC83. Channel 2 uses a much smaller coupling cap for a brighter, leaner voice. Both mix into a second ECC83 gain stage and cathode follower driving Treble, Middle and Bass, and an ECC83 inverter with Presence drives two EL34s, making it a common choice for guitarists.

• Made in: UK
• Wattage: 50W
• Channels: 2
• Preamp tubes: 3× ECC83
• Power tubes: 2× EL34

Tags: british, vintage, el34, two-channel, 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.