Gibson BR-3 - Microphone preset

Verified · 86/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The BR-3 is a post-war Gibson amplifier for lap steel, with a microphone input on its own 7B4 stage and volume, and two instrument inputs sharing a second volume. Both mix into a second 7B4, then a tone control and a 6J5 driver feed an interstage transformer that splits the phase for a push-pull pair of 6V6s. A 5Z4 rectifier powers it, with an optional 6K5 supply for an electro-dynamic speaker field coil.

• Made in: USA
• Wattage: 15W
• Channels: 2
• Preamp tubes: 2× 7B4, 1× 6J5
• Power tubes: 2× 6V6

Tags: american, vintage, clean, 6v6.

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.