Marshall Super Lead 1959 MkII (US 6550) - High Treble preset

Verified · 85/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

This is the US (Unicord) version of the 1959 Super Lead Mark II from 1970, fitted with 6550 output valves instead of EL34s for the American market. Four inputs feed two ECC83 channels with their own volumes, mixed into a second ECC83 gain stage and cathode follower driving Treble, Middle and Bass, with no master. An ECC83 inverter with Presence drives four 6550s off a silicon bridge, for a tighter, cleaner low end than the EL34 version.

• Made in: UK
• Wattage: 100W
• Channels: 2
• Preamp tubes: 3× ECC83
• Power tubes: 4× 6550

Tags: british, vintage, plexi, crunch, 6550, high-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.