Radford STA25 Renaissance preset

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

The Radford STA25 Renaissance is a later reissue of Radford's STA25 stereo valve power amplifier, a clean, low-distortion British hi-fi design with no preamp or tone controls. Each identical side has a direct-coupled ECC88 input stage, a 6U8A cathode-coupled phase splitter with a balance control, and a push-pull pair of 6550As rather than the original's EL34s, with global feedback. Per-channel bias adjustment and a push-to-test bias indicator complete it.

• Made in: UK
• Channels: 1
• Preamp tubes: 2× ECC88, 2× 6U8A
• Power tubes: 4× 6550A

Tags: british, reissue, 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.