Marshall JMP 1987 Lead Mk II (6550) - High Treble preset

Verified · 90/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The 1970 Marshall 1987 Lead Mark II is the 50-watt plexi-era head in its Unicord (US-market) form, fitted with a pair of 6550 output tubes instead of EL34s. It has four inputs across two channels, an ECC83 gain stage and driver into a treble/bass/middle stack, and an ECC83 long-tailed-pair phase inverter. The 6550s give a firmer low end and more clean headroom than the EL34 version.

• Made in: UK
• Wattage: 50W
• Channels: 2
• Preamp tubes: 3× ECC83
• Power tubes: 2× 6550

Tags: british, vintage, 6550, mid-wattage, 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.