Ampeg B-15N (1968) PortaFlex - Channel One preset

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

This DIY Guitar Archive schematic documents both the B-12N and B-15N PortaFlex models, Channel One, highlighting their shared circuit topology. The B-12N and B-15N differ primarily in speaker size. Both deliver the warm, punchy Ampeg bass tone that defined the Motown and soul studio sound of the 1960s.

• Years produced: 1961–1969
• Made in: USA
• Wattage: 25W
• Channels: 2
• Preamp tubes: 3× 12AX7
• Power tubes: 2× 6L6

Known for: James Jamerson, Bob Babbitt, Carol Kaye.

Heard on: What's Going On — Marvin Gaye (1971).

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.