Supro Thunderbolt S6420 preset

Verified · 90/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The 1965 Supro Thunderbolt S6420-TR is the tube-rectified version of the Thunderbolt, a 1×15 combo with just Volume and Tone. Two inputs feed one half of a 12AX7 (the other triode is unused), then the Volume and Tone controls and a second 12AX7 whose halves give a gain stage and a cathodyne phase splitter. Two cathode-biased 6L6GCs with a shared cathode resistor and no negative feedback drive a 15-inch Jensen, from a 5U4 rectifier. 1964–65 amps were covered in blue with a valve rectifier; the 1966 model went black with a solid-state rectifier.

Known for: Jimi Hendrix.

Tags: american, vintage, 6l6, bass, crunch.

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.