Ampeg M-18 - Accordion preset

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

The Ampeg M-18 is a two-channel tube combo for guitar and accordion: one channel serves four instrument inputs and the other two accordion inputs, each built on half a 6SL7 with its own volume and tone control. A second 6SL7 is the tremolo oscillator with speed, intensity and a footswitch, and a third 6SL7 provides gain and phase inversion for a push-pull pair of 6L6s, with feedback from the speaker and a 5U4 rectifier.

Tags: american, vintage, 6l6, tremolo, two-channel, mid-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.