National-Dobro Model 21 - Main preset

Close · 75/100 confidence. Most values readable. Minor gaps filled by inference from similar circuits.

The National-Dobro Model 21 is a pre-war American tube guitar amplifier from National-Dobro of Chicago, dating from the earliest era of electric guitar amplification. National-Dobro was at the forefront of developing both electric guitars and the amplifiers needed to play them in the mid-1930s. These exceptionally rare pre-war amps are significant historical artifacts for guitar historians and collectors.

• Years produced: 1935–1942
• Made in: USA
• Channels: 1

Tags: american, vintage.

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.