Supro 6420 Thunderbolt - Main preset

Close · 76/100 confidence. Most values readable. Minor gaps filled by inference from similar circuits.

The Supro 6420 Thunderbolt is a 35-watt bass and instrument combo amplifier originally designed for bass players but favored by guitarists seeking its distinctive dirty clean and natural compression. Its unique cathode-biased 6550 output tube configuration produces a spongy, complex overtone structure different from conventional 6L6 or EL34 amps. The Thunderbolt became highly collectible after Jack White prominently used it in the White Stripes.

• Years produced: 1962–1968
• Made in: USA
• Wattage: 35W
• Channels: 1
• Preamp tubes: 2x 12AX7
• Power tubes: 1x 6550

Known for: Jack White.

Tags: american.

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.