Ampeg SVT Power Amplifier (1969-71, 6146B) - Normal preset

Close · 78/100 confidence. Most values readable. Minor gaps filled by inference from similar circuits.

The original 1969–1971 Ampeg SVT (Super Vacuum Tube) was the amplifier that defined the standard for professional bass amplification. This earliest version used six 6146B beam-tetrode power tubes — a tube type borrowed from radio transmitter design — producing 300 watts of thunderous, uncolored bass power. Designed by Bill Hughes and Roger Cox at Ampeg, the SVT was first publicly used by the Rolling Stones on their 1969 US tour, establishing it immediately as the professional touring standard.

• Years produced: 1969–1971
• Made in: USA
• Wattage: 300W
• Channels: 2
• Preamp tubes: 6× 12AX7, 2× 12DW7
• Power tubes: 6× 6146B

Known for: John Entwistle, Geezer Butler, Lemmy Kilmister, Geddy Lee.

Heard on: Black Sabbath — Black Sabbath (1970).

Tags: american.

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.