Marshall Unicord Model 1978 Circa1970 preset

Verified · 80/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The Marshall Major 1978U is the bass variant of the 200W Major amplifier, sharing the KT88-powered circuit with modified voicing for bass guitar. Its extreme headroom and clean transient response made it one of the most powerful bass amplifiers available in the early 1970s.

• Years produced: 1967–1974
• Made in: UK
• Wattage: 200W
• Channels: 2
• Preamp tubes: 4× ECC83
• Power tubes: 4× KT88

Tags: british, vintage, high-power, 200w.

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.