Supro Thunderbolt S6420 (TR) - Normal preset

Verified · 80/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The Supro Thunderbolt S6420 with tube rectifier is the earlier, softer-responding version of this iconic Valco design, using a tube rectifier for a characteristic sag and compression under high-demand playing. The tube rectifier contributes warmth and a more vintage feel to the already characterful Thunderbolt circuit. This is the version most commonly associated with the raw, compressed tones heard on early hard rock recordings.

• Years produced: 1962–1965
• Made in: USA
• Wattage: 35W
• Channels: 2
• Preamp tubes: 2× 12AX7
• Power tubes: 2× 6L6

Known for: Jimmy Page.

Heard on: Communication Breakdown — Led Zeppelin (1969).

Tags: american, vintage, 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.