Univox U-1221 - Reverb preset

Verified · 89/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The U-1221 is a two-channel Univox valve combo of the early 1970s, not a solid-state amp. Each channel has Bright and Normal inputs, a 12AX7 triode stage, its own volume and its own tone control. A 6AN8 drives the spring reverb with a 12AX7 recovery stage, depth control and footswitch, and a 12AX7 tremolo works through a 12AU7 bias modulator. A second 6AN8 provides gain and phase inversion, driving two fixed-bias 6L6GCs at about 660 V.

• Made in: Japan
• Wattage: 50W
• Channels: 2
• Preamp tubes: 2× 12AX7, 1× 12AU7, 2× 6AN8
• Power tubes: 2× 6L6GC

Tags: japanese, vintage, 6l6, reverb, tremolo, two-channel.

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.