THD UniValve preset

Verified · 93/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The THD UniValve is a roughly 15-watt single-ended class-A head built around one output tube that can be a 6L6, EL34 or 6550 without rebiasing. Two 12AX7As give four gain stages with treble, bass and attitude controls and no negative feedback, plus a built-in Hotplate attenuator and a line out.

• Introduced: 2001
• Made in: USA
• Wattage: 15W
• Channels: 1
• Preamp tubes: 2× 12AX7A
• Power tubes: 1× 6L6/EL34/6550

Tags: american, boutique, class-a, crunch, low-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.