Supro 6420 Thunderbolt Bass Amp (1966) - Normal preset

Verified · 91/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The Supro 6420 Thunderbolt Bass Amp was Valco's high-powered offering designed for bass players, featuring a 35-watt output and a configuration optimized for low-frequency reproduction. Despite its bass designation, the Thunderbolt's raw, bright American character made it attractive for guitar players seeking aggressive tones as well. Valco's distinctive construction methods give all Thunderbolt variants a unique sonic signature unlike any contemporary amplifier.

• Years produced: 1966–1968
• 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.