Harmony H-311 - Channel 1 preset

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

The Harmony H-311 is a late-1960s reverb and tremolo combo with two channels, each with two inputs and its own volume and tone, plus a channel selector. A 12AX7 serves both channel preamps, a 6BM8 drives a Hammond spring reverb recovered by another 12AX7, and a 6AU6 runs the tremolo (speed and modulation). A 12AX7 gain stage and cathodyne feed two cathode-biased 7591s on a GZ34. Reverb and tremolo are footswitchable.

• Made in: USA
• Wattage: 30W
• Channels: 2
• Preamp tubes: 3× 12AX7, 1× 6BM8, 1× 6AU6
• Power tubes: 2× 7591

Tags: vintage, reverb, tremolo, 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.