Gibson GA-85 - Channel I preset

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

The GA-85 is a 1950s two-channel Gibson amp, two inputs per channel, each channel on half a 12AX7. Channel I has volume, treble and bass controls; channel II has volume and a single tone control. A second 12AX7 adds gain and works as a split-load phase inverter for a push-pull pair of 5881 output tubes, with a valve regulator on the supply, a 5V4G rectifier, a standby switch and a monitor jack.

• Made in: USA
• Wattage: 25W
• Channels: 2
• Preamp tubes: 2× 12AX7
• Power tubes: 2× 5881

Tags: american, vintage, clean, 6l6.

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.