Marshall Major PA 1966 preset

Verified · 84/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The Marshall 1966 Major PA is a 200-watt valve PA head, the PA version of the Major, shown here in its 1970 form. Eight inputs in four pairs run into two ECC83s, each pair with its own volume and identical networks, mixed into a third ECC83 gain stage and cathode follower driving Treble, Middle and Bass with Presence. An ECC82 long-tail inverter drives four KT88s off a silicon bridge, giving huge clean headroom.

• Made in: UK
• Wattage: 200W
• Channels: 1
• Preamp tubes: 3× ECC83, 1× ECC82
• Power tubes: 4× KT88

Tags: british, vintage, kt88, high-wattage, clean.

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.