DIY AO-39 Conversion preset

Verified · 84/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

A DIY conversion of a Hammond AO-39 organ power amp into a guitar amp modelled loosely on a Vox AC15. An EF86 pentode input with a 6-way voicing-cap switch and a Volume feeds a 12AX7 long-tailed-pair inverter with a Cut control, driving a cathode-biased pair of EL84s on the original Hammond transformers with a 5Y3 rectifier. The file also shows an alternate Marshall '18 Watt'-style version on the same chassis and the original organ amp.

• Channels: 1
• Preamp tubes: 1× EF86, 1× 12AX7
• Power tubes: 2× EL84

Tags: diy, el84, chime, breakup, class-a.

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.