Bogen CHB-20A preset

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

The Bogen CHB-20A is a 20-watt tube PA amplifier. A 6EU7 dual triode amplifies the microphone input, with mic volume and master volume, while two auxiliary line inputs share an aux volume control. Bass and treble controls follow, then the triode halves of two 6GW8/ECL86s act as amplifier and paraphase inverter for their pentode halves, run push-pull with fixed bias and negative feedback, with 70 V line and 4, 8 and 16 ohm taps.

• Made in: USA
• Wattage: 20W
• Channels: 1
• Preamp tubes: 1× 6EU7
• Power tubes: 2× 6GW8 (ECL86)

Tags: american, vintage, clean, low-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.