Gibson Mastertone preset

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

The Mastertone is an early single-ended Gibson amp of the late 1930s or 1940s, about as simple as a guitar amp gets: one input, a single volume control, and no tone control or negative feedback. A 6SJ7 pentode preamp drives a single cathode-biased 6V6 into the output transformer and speaker. A 5Y3 rectifier supplies the power, with the speaker's field coil doubling as the filter choke.

• Made in: USA
• Wattage: 5W
• Channels: 1
• Preamp tubes: 1× 6SJ7
• Power tubes: 1× 6V6

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

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.