Sunn Sceptre (1971) preset

Verified · 91/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The Sunn Sceptre is a tube head from Sunn's late-1960s and early-1970s range, closely related to the 100S and Sentura II. Normal and Bright input pairs feed a two-stage 12AX7 preamp with one Volume, a photocell tremolo module with a transistor oscillator, Depth, Rate and footswitch, and Treble, Bass and Contour controls with a three-position mid-boost switch. A 12AU7 drives a spring reverb with transistor recovery. A 6AN8 gain stage and inverter drive two fixed-bias 6550s from a GZ34 rectifier, with feedback from the output.

• Made in: USA
• Wattage: 60W
• Channels: 1
• Preamp tubes: 1× 12AX7, 1× 12AU7, 1× 6AN8
• Power tubes: 2× 6550

Tags: american, vintage, 6550, reverb, tremolo.

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.