National-Dobro Model B - Microphone preset

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

The Model B is a late-1930s National-Dobro amplifier from the first generation of amps built for electric steel and Spanish guitars, dating from October 1938. Four inputs (three instrument plus a mic) feed two 6N7 dual-triode stages, each pair with its own volume control, then mix into a third 6N7 and a 6N7 phase inverter driving a push-pull pair of 6L6s. A 5V4G rectifier and a field-coil speaker complete it; there is no tone control.

Tags: american, vintage, two-channel.

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.