Radford STA15 preset

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

The Radford STA15 is a British stereo valve power amplifier rated 15 watts per channel, for home hi-fi, with a mono MA15 version. Each identical side has an EF86 pentode input stage, a 6U8 cathode-coupled phase splitter and a cathode-biased push-pull pair of EL34s into an output transformer with 4, 8 and 16 ohm taps, each with its own feedback network. A GZ34 valve rectifier and choke supply both sides. There is no preamp.

• Made in: UK
• Wattage: 15W
• Channels: 1
• Preamp tubes: 2× EF86, 2× 6U8
• Power tubes: 4× EL34

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