Gibson GA-75 (early) - Channel 2 preset

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

This early GA-75 is a 1940s Gibson combo with two channels: a single-input channel on a 6SJ7 pentode and a four-input channel on a pair of 6SC7 twin triodes, each channel with its own volume. The channels mix into two tone controls, then a third 6SC7 works as a paraphase inverter driving a push-pull pair of 6L6GA tubes on a 5V4G rectifier into one speaker. There is no master volume.

• Made in: USA
• Wattage: 25W
• Channels: 2
• Preamp tubes: 1× 6SJ7, 3× 6SC7
• Power tubes: 2× 6L6GA

Tags: american, vintage, clean, 6l6.

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.