What tubes does the Harmony H-304A use?

The Harmony H-304A uses 12AX7 preamp tubes and 6V6 power tubes.

When was the Harmony H-304A produced?

The Harmony H-304A was produced 1963–1968.

Harmony H-304A preset

Verified · 85/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The Harmony H304A is a revised version of the H304 incorporating minor circuit changes, likely to address component availability or reliability issues during production. It shares the two-channel layout and warm, simple tonal character of the H304. Both versions are typical of the Chicago-made student amplifier tradition of the early 1960s.

Years produced: 1963–1968
Made in: USA
Wattage: 10W
Channels: 2
Preamp tubes: 12AX7
Power tubes: 6V6

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.