Marshall Valvestate 20 8020 - Boost preset

Verified · 93/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The Valvestate 20 (8020) is a 20-watt practice combo from Marshall's first-generation Valvestate range, dated 1991. Despite the range name, this drawing has no valve: it is all op-amps. The Normal channel has Gain, Treble and Bass; the footswitchable Boost channel has its own Gain with LED clipping, Contour, Presence and Volume. Both share spring reverb into an LM1875 power amp IC, with headphone and DI outputs.

Tags: british, solid-state, crunch, low-wattage, two-channel.

Schematic-derived preset files for the Neural DSP Quad Cortex and 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.