Gibson GA-78 Stereo - Channel 1 preset

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

The GA-78 is a two-channel Gibson stereo amplifier: each channel has two inputs, a phono jack and its own tone and volume, and a stereo input feeds both. Each channel has its own 6EU7 inverter driving a cathode-biased push-pull pair of 6BQ5 (EL84) tubes into its own speaker, with a stereo/mono switch. A 6EU7 tremolo has frequency, depth and a footswitch, and power comes from a separate solid-state supply chassis.

Tags: american, vintage, clean, stereo, tremolo, el84.

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.