Marshall VBA400 preset

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

The VBA400 is a 400-watt all-valve bass head from 1998 with eight 6550 output valves, one of the most powerful valve bass amps of its time. Passive and active inputs feed ECC83 gain stages with Gain, a switchable Contour, Treble, Middle, Bass, Bright and Deep, then a Master; an ECC82 drives the output stage. It adds an effects loop, tuner out, a pre/post-EQ balanced DI with earth lift, tune-up mute and fan speed switching.

• Made in: UK
• Wattage: 400W
• Channels: 1
• Preamp tubes: 3× ECC83, 1× ECC82
• Power tubes: 8× 6550

Tags: british, bass, 6550, 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.