Ampeg B-15NA / B-12NA - Channel 2 preset

Close · 78/100 confidence. Most values readable. Minor gaps filled by inference from similar circuits.

The B-15NA/B-12NA Channel 1 documents the standard input path of these early PortaFlex models. The NA designation indicates a specific early circuit revision. These are among the earliest production PortaFlex schematics, representing the original B-15N design before later NC and NF revisions.

• 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.