Gibson Les Paul Junior GA-5 (6SJ7) preset

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

This Les Paul Junior GA-5 is the small Gibson student amp sold as the companion to the Les Paul Junior guitar. Two inputs feed a 6SJ7 pentode preamp, followed by a single volume control and no tone control, driving a single-ended, cathode-biased 6V6 into one speaker, with a 5Y3GT rectifier. It makes about 4 watts and breaks up easily at low volume. This octal-preamp circuit differs from the 12AX7-preamp GA-5.

• Made in: USA
• Wattage: 4W
• Channels: 1
• Preamp tubes: 1× 6SJ7
• Power tubes: 1× 6V6

Tags: american, vintage, low-wattage, practice, 6v6, class-a.

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.