Gibson GA-25 preset

verified · 90/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The GA-25 is a late-1940s Gibson combo with one high-gain input and three instrument inputs, all feeding a single 6SJ7 pentode preamp with one volume and one tone control. Two 6J5 triodes form a paraphase inverter driving a push-pull pair of 6V6GT tubes on a 5Y3GT rectifier, and the output transformer feeds an 8-inch and a 12-inch speaker together.

• Made in: USA
• Channels: 1
• Preamp tubes: 1× 6SJ7, 2× 6J5
• Power tubes: 2× 6V6GT

Tags: american, vintage, clean, 6v6.

Schematic-derived preset files for the Neural DSP Quad Cortex and 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.