Harmony H-400A preset

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

The H-400A is a small Harmony practice amp built on the All-American-Five topology used in table radios. Three inputs share a volume control into a 12AU6 pentode preamp, and a second pot on the output-tube grid shapes the tone. A single-ended, cathode-biased 50C5 beam tube with feedback from its plate drives a 3.2-ohm speaker, and a 35W4 half-wave rectifier runs straight off the mains with no power transformer, for about 3 to 4 watts.

• Made in: USA
• Wattage: 4W
• Channels: 1
• Preamp tubes: 1× 12AU6
• Power tubes: 1× 50C5

Tags: american, vintage, practice, low-wattage.

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.