Ampeg SVT Power Amplifier (6146B version) - Main preset

Verified · 80/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The SVT Power Amplifier with 6146B tubes documents the original output stage of Ampeg's legendary bass head. Six 6146B beam tetrodes produce 300 watts with a distinctive hard, aggressive character. The 6146B version is the earliest and rarest SVT configuration, representing the original vision for the world's most powerful production bass amplifier.

• Years produced: 1969–1971
• Made in: USA
• Wattage: 300W
• Channels: 1
• Preamp tubes: 2× 12AU7
• Power tubes: 6× 6146B

Known for: Paul McCartney, Geddy Lee, John Entwistle, Lemmy Kilmister, Geezer Butler, Cliff Burton.

Heard on: Won't Get Fooled Again — The Who (1971).

Tags: bass, american, vintage, high-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.