Univox U-250PB preset

Verified · 92/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The U-250PB is a small solid-state Univox piggyback bass amp from around 1969, with a 1×15-inch 4-ohm cabinet. Two inputs feed a 250K volume and a two-transistor preamp with a single tone control, followed by a driver transistor and a complementary output pair with overall negative feedback, capacitor-coupled to the speaker. A bridge rectifier on a 31 V winding supplies about 41 V. The drawing references 19 watts of output.

• Made in: Japan
• Channels: 1

Tags: japanese, solid-state, vintage.

Schematic-derived preset files for the Neural DSP Quad Cortex and 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.