Radford STA25 preset

Verified · 88/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The Radford STA25 is a British stereo valve power amplifier rated 25 watts per channel, with a mono MA25 version. Each identical side has an EF86 pentode input stage, a 6U8 cathode-coupled phase splitter and a fixed-bias push-pull pair of EL34s with bias test points, into an output transformer with 4, 8 and 16 ohm taps. A silicon-diode bridge and choke supply both sides. A clean hi-fi design with no preamp, it is also used as a guitar power amp.

Tags: british, vintage, el34, stereo, power-amp, clean.

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.