What tubes does the Harmony H-303A use?

The Harmony H-303A uses 12AX7 preamp tubes and 6V6 power tubes.

When was the Harmony H-303A produced?

The Harmony H-303A was produced 1960–1965.

Harmony H-303A preset

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

The Harmony H303A is a small student combo from the early 1960s offering a single-ended tube circuit with modest output. Like most Harmony amplifiers, it was priced to accompany Harmony's inexpensive guitars and aimed at the student and hobbyist market. The tone is warm and slightly compressed, with limited headroom before natural breakup.

Years produced: 1960–1965
Made in: USA
Wattage: 8W
Channels: 1
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.