Ampeg B-12NC / B-15NC Portaflex - Channel 1 preset

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

The Ampeg B-12-NC and B-15-NC are one Portaflex flip-top bass circuit. The two models differ only in speaker: a 12-inch in the B-12-NC and a 15-inch in the B-15-NC. Each of the two channels has 6SL7 stages around a bass/treble network. A 6SL7 paraphase inverter drives a cathode-biased pair of 6L6GCs, with a 5AR4 rectifier. It has the round, warm, compressed Portaflex bass tone.

• Years produced: 1964–1965
• Made in: USA
• Wattage: 25W
• Channels: 2
• Preamp tubes: 3× 6SL7
• Power tubes: 2× 6L6GC

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

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.