Ampeg B-12NA / B-15NA - Channel 1 preset

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

The B-12NA and B-15NA are early PortaFlex models sharing the NA circuit designation, indicating a specific production revision with updated component values. Channel 1 provides the warm, punchy bass tone foundational to the PortaFlex legacy. These early models are among the most collectible of the PortaFlex series.

• Years produced: 1960–1964
• Made in: USA
• Wattage: 25W
• Channels: 2
• Preamp tubes: 3× 12AX7
• Power tubes: 2× 6L6

Known for: James Jamerson.

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

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.