Hiwatt STA400 Slave preset

Close · 74/100 confidence. Most values readable. Minor gaps filled by inference from similar circuits.

The Hiwatt STA400 is a 400-watt slave power amplifier with no preamp or tone controls, built to be driven by a separate head or preamp for very large stage rigs, and the basis of the DR405 head. An ECC83 input stage with feedback feeds an ECC81 long-tailed-pair inverter, then ECC83 cathode followers drive six fixed-bias KT88s, three per side, into a Partridge transformer from roughly 700-volt solid-state bridge supplies.

• Made in: UK
• Wattage: 400W
• Channels: 1
• Power tubes: 6× KT88

Tags: british, power-amp, 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.