Supro 6420 Thunderbolt Bass Amp (1965, S6420) - Normal preset

Verified · 88/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The Supro 6420 Thunderbolt Bass Amp (1965, S6420) represents the mid-decade variant of the iconic Thunderbolt series, reflecting production refinements made during Valco's peak manufacturing period. At 35 watts through two 6L6 tubes, it delivers the same raw, bold American character that made the Thunderbolt name famous. The 1965 vintage point is significant as it captures the amp before the later cost-reduction changes that affected some Valco designs.

• Years produced: 1965
• 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.