Ampeg SVT (1969, 6146B) - Channel 2 preset

Verified · 92/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The original 1969 Ampeg SVT, the 300-watt bass head with six 6146B beam tetrodes in push-pull parallel, before production moved to 6550s. The preamp gives two channels, each with bright and normal inputs, volume, bass and treble, Ultra-Hi and Ultra-Lo switches and an inductor-based mid-range selector on 12DW7, 12AX7 and 6C4 tubes. In the power amp a 12DW7 phase inverter and two 12BH7 drivers feed the output tubes, with fixed bias, a balance control and a baffle interlock.

• Years produced: 1969–1970
• Made in: USA
• Wattage: 300W
• Channels: 2
• Preamp tubes: 4× 12DW7, 1× 12AX7, 1× 6C4, 2× 12BH7
• Power tubes: 6× 6146B

Known for: Bill Wyman.

Heard on: Midnight Rambler (Live at Madison Square Garden) — The Rolling Stones (1969).

Tags: american, vintage, bass, high-wattage, two-channel.

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.