Supro 6420-TR Thunderbolt Bass Amp (1965 variant, current production O preset

Verified · 87/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The Supro 6420-TR Thunderbolt Bass Amp (1965 variant, current production) represents either the original or a faithfully reproduced version of this iconic Valco circuit. The tube rectifier version is particularly valued for its characteristic sag and compression, contributing to the warm, organic response that distinguishes the Thunderbolt from solid-state rectified designs. This variant captures the Thunderbolt at its most vintage-voiced.

• Years produced: 1965–1968
• Made in: USA
• Wattage: 35W
• Channels: 2
• Preamp tubes: 2× 12AX7
• Power tubes: 2× 6L6

Tags: american, vintage, bass.

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.