Gibson GA-20 (1959, 12AX7) - Instrument preset

Verified · 89/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

This late-1950s version of Gibson's GA-20 uses 12AX7s throughout. A Mic channel and an Instruments channel each have two inputs on their own 12AX7 and their own volume control, followed by a shared tone control. A third 12AX7 works as a paraphase inverter driving a cathode-biased push-pull pair of 6V6GT tubes, with a 5Y3 rectifier, into one 8-ohm speaker for about 14 watts. A small tweed-era Gibson that breaks up early.

• Made in: USA
• Wattage: 14W
• Channels: 2
• Preamp tubes: 3× 12AX7
• Power tubes: 2× 6V6GT

Tags: american, vintage, 6v6, breakup, two-channel, low-wattage.

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.