Ampeg B-12NB / B-15NB (alt) - Channel 1 preset

Verified · 82/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The B-12NB and B-15NB (alt) share a circuit using the NB revision designation with component updates. Channel 1 delivers the classic PortaFlex bass tone in these 12-inch and 15-inch speaker variants respectively. The B suffix indicates a cabinet configuration, while the N denotes the standard circuit series.

• Years produced: 1962–1966
• Made in: USA
• Wattage: 25W
• Channels: 2
• Preamp tubes: 3× 12AX7
• Power tubes: 2× 6L6

Tags: bass, american, vintage, low-wattage, clean.

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.