Ampeg B-12XT / B-18X Portaflex - Channel 2 preset

Verified · 91/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The Ampeg B-12-XT and B-18-X share one Portaflex flip-top circuit (1967 drawing). They differ only in the speaker connection, with the B-18-X built around an 18-inch speaker. Two channels each have volume, bass and treble. The amp has spring reverb and Ampeg's VM-1 vibrato module. A 7199 phase inverter drives a push-pull pair of 7027As, with a 5AR4 rectifier.

• Made in: USA
• Wattage: 50W
• Channels: 2
• Preamp tubes: 4× 12AX7, 1× 7199, 1× 6CG7
• Power tubes: 2× 7027A

Tags: american, vintage, reverb, vibrato, 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.