Stromberg-Carlson AU-33 preset

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

Stromberg-Carlson's AU-33 valve PA amplifier from around 1951. Three 6SJ7 mic stages and a phono input mix through a 6SF5 into a 6N7 driver and phase inverter, then a push-pull pair of 6L6Gs with a 5U4G rectifier. It is an octal-era American PA amp that players adapt for warm, round 6L6 guitar and harmonica tones.

• Made in: USA
• Wattage: 25W
• Channels: 1
• Preamp tubes: 3× 6SJ7, 1× 6SF5, 1× 6N7
• Power tubes: 2× 6L6G

Tags: american, vintage, 6l6, mid-wattage, clean.

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.