Gibson GA-9 preset

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

The GA-9 is a simple single-channel Gibson student amp of the mid-to-late 1950s, the successor to the BR-9, with two inputs and only a volume control, no tone control. A 6SJ7 pentode preamp drives a pair of 6V6GT output tubes with no separate phase-inverter valve: the pair shares a cathode resistor and splits phase through it, cathode-biased. A 5Y3GT rectifier supplies the power, and the speaker field coil doubles as the supply choke.

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.