Valco 6400 preset

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

The Valco 6400 is a small push-pull tube combo. Three inputs (one Treble-voiced, two Bass-voiced) feed a 12AX7 first stage, then a Volume and a Tone control, a second 12AX7 gain stage and a paraphase inverter. Two 6973 output tubes share a cathode-bias resistor with no negative feedback, driving a single 10-inch 8-ohm speaker from a 5Y3GT rectifier. The 6973 pair sets it apart from the more common 6V6 designs.

• Made in: USA
• Channels: 1
• Preamp tubes: 2× 12AX7
• Power tubes: 2× 6973

Tags: american, vintage.

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.