Selmer Thunderbird Twin 50 - Selectortone preset

Verified · 83/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The Thunderbird Twin 50 is the fixed-bias 50-watt version of Selmer London's croc-skin Thunderbird Twin from the mid-1960s, sharing its front end with the Twin 30. Channel 1 has an ECC83 input, the push-button tone selector and a 6BR8 stage with its own volume; channel 2 has treble, bass and its own 6BR8 and volume. ECC81 stages drive and recover a spring reverb, the vibrato has an EM84 eye, and an ECC83 inverter drives two EL34s from a GZ34.

• Made in: UK
• Wattage: 50W
• Channels: 2
• Preamp tubes: 3× ECC83, 2× 6BR8, 1× ECC81, 1× ECC82
• Power tubes: 2× EL34

Tags: british, vintage, 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.