Ampeg SVT - Channel 1 preset

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

This is the 6550 Ampeg SVT of the 1970s, drawn here in Ampeg's 1977 service manual: a 300-watt all-tube bass head. Two channels with bright and normal inputs have volume, bass, treble, Ultra-Lo/Ultra-Hi switches and an inductor-based midrange selector, and a 12DW7 inverter with 12BH7 drivers runs six 6550s off a 695V solid-state rectified supply. The first SVTs of 1969 used 6146B output tubes; the 6550 version replaced them in the early 1970s.

• Made in: USA
• Wattage: 300W
• Channels: 2
• Preamp tubes: 1× 12AX7, 4× 12DW7, 1× 6C4, 2× 12BH7
• Power tubes: 6× 6550

Known for: Bill Wyman, Geddy Lee, Scott Reeder.

Heard on: Animate — Rush (1993); Gardenia — Kyuss (1994).

Tags: american, vintage, bass, 6550, two-channel, 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.