Marshall JMP Tremolo 1987T - High Treble preset

Verified · 89/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The 1987T is the 50-watt plexi Lead head with an added valve tremolo, shown here in its 1970 US form. Four inputs feed two ECC83 channels with their own volumes, mixing into a second ECC83 gain stage and cathode follower driving Treble, Middle and Bass. A fourth ECC83 phase-shift oscillator with Speed and Intensity, transistor-switched by footswitch, adds tremolo; an ECC83 inverter with Presence drives two EL34s, with a half-power switch.

• Made in: UK
• Wattage: 50W
• Channels: 2
• Preamp tubes: 4× ECC83
• Power tubes: 2× EL34

Tags: british, vintage, plexi, tremolo, el34, mid-wattage, 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.