Selmer Thunderbird 50 Mk II preset

Verified · 90/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The Thunderbird 50 Mk II is a British Selmer valve amp from the 1960s line that competed with Vox and Marshall. An ECC83 input feeds a push-button tone selector with volume, treble and bass, then an ECC83 gain stage. A 6BR8 drives the spring reverb with ECC83 recovery and level, and an ECC83 oscillator runs a light-dependent-resistor tremolo. An ECC83 long-tail inverter with presence drives two fixed-bias EL34s from a GZ34 rectifier.

• Made in: UK
• Wattage: 50W
• Channels: 1
• Preamp tubes: 4× ECC83, 1× 6BR8
• Power tubes: 2× EL34

Tags: british, vintage, el34, reverb, tremolo, mid-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.