Bogen Challenger CHA-20 preset

Verified · 90/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The Challenger CHA-20 is a late-1950s Bogen tube PA amplifier with a 12AX7 mic and phono preamp, bass and treble controls, a 12AX7 driver and paraphase inverter, and a push-pull pair of 6V6GTs. In stock form it is a 20-watt PA amp, but its 6V6 output stage and sturdy iron make it a popular platform for harmonica and guitar amp conversions.

• Made in: USA
• Wattage: 20W
• Channels: 1
• Preamp tubes: 2× 12AX7
• Power tubes: 2× 6V6GT

Tags: american, vintage, 6v6.

Schematic-derived preset files for the Neural DSP Quad Cortex and 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.