Ampeg B-25B - Channel 2 preset

Verified · 88/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The Ampeg B-25B is the early-1970s revision of the B-25 tube bass head, built when Ampeg was a division of Magnavox. Each of its two channels has Bright and Normal inputs, a 12AX7 and its own Volume, Bass and Treble, with Ultra Hi and Ultra Lo switches. A 7199 gain stage and cathodyne splitter drive a fixed-bias push-pull pair of 7027As for about 55 watts, with a 5AR4 rectifier, standby and an external-amp jack.

• Made in: USA
• Wattage: 55W
• Channels: 2
• Preamp tubes: 2× 12AX7, 1× 7199
• Power tubes: 2× 7027A

Tags: american, vintage, bass, two-channel, high-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.