Gibson GA-1RT preset

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

The GA-1RT is a small 1960s Gibson practice combo with two inputs, a volume control and no tone control. A passive electro-mechanical reverb unit sits at the input with a footswitch, and the triode half of the 6BM8 runs a phase-shift tremolo with a rate control. Both halves of a 12AX7 provide the gain into the single-ended, cathode-biased 6BM8 pentode with negative feedback from the speaker, on a 5Y3GT rectifier, for about 4 watts.

• Made in: USA
• Wattage: 4W
• Channels: 1
• Preamp tubes: 1× 12AX7
• Power tubes: 1× 6BM8

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

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.