Bogen CHA-20 Blues Special (modified) - Normal preset

Verified · 82/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The Bogen CHA-20 Blues Special is a modified version of the Bogen CHA-20 PA amplifier, customized with reverb and vibrato circuitry to create a blues and guitar-focused amplifier from the vintage commercial platform. Bogen CHA series amps were popular subjects for guitar amp modification due to their robust transformer quality and receptive circuit topology. This Blues Special variant demonstrates the creative reinterpretation that vintage Bogen PA amps have inspired among the DIY amp building community.

Tags: american, vintage.

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.