Ampeg SVT Power Amp (6550A) - Normal preset

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

The SVT Power Amp schematic with 6550A tubes documents the standard production output stage used throughout most of the SVT's production run. The 6550A became the preferred output tube after early 6146B versions, offering improved reliability and slightly warmer low-end extension at the SVT's demanding operating conditions.

• Years produced: 1969–present
• Made in: USA
• Wattage: 300W
• Channels: 1
• Preamp tubes: 2× 12AU7
• Power tubes: 6× 6550

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

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.