Gibson Les Paul GA-40 (6SJ7) - Microphone preset

Verified · 90/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The early Les Paul GA-40 used octal 6SJ7 pentodes for its separate microphone and instrument preamps and for the driver stage. A 6SN7 works as both inverter and tremolo, a 6V6 runs the tremolo circuit, and a pair of 6V6GT output tubes on a 5V4G rectifier produce roughly 14 watts. This is the warmer, looser pentode-preamp version that came before the later 5879 redesign.

• Made in: USA
• Wattage: 14W
• Channels: 2
• Preamp tubes: 3× 6SJ7, 1× 6SN7, 1× 6V6
• Power tubes: 2× 6V6GT

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

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.