What tubes does the Hiwatt 400W Sta400 use?

The Hiwatt 400W Sta400 uses 2× ECC83 (12AX7) preamp tubes and 16× EL34 power tubes.

When was the Hiwatt 400W Sta400 produced?

The Hiwatt 400W Sta400 was produced 1973–1981.

Hiwatt 400W Sta400 preset

Verified · 80/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The Hiwatt STA400 is a 400-watt pure power amplifier built for professional PA and monitoring systems at a scale that was almost unprecedented in the early 1970s. Sixteen EL34 tubes are run in carefully matched pairs, handwired point-to-point in the Hiwatt tradition, to deliver clean, high-fidelity amplification across the full audio spectrum. The STA400 was used by touring sound companies and select artists who required absolute reliability and maximum headroom for festival-scale reinforcement, and its construction quality means many examples remain fully operational decades later.

Years produced: 1973–1981
Made in: UK
Wattage: 400W
Channels: 1
Preamp tubes: 2× ECC83 (12AX7)
Power tubes: 16× EL34

Tags: british, clean, vintage.

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.