Standel PB-25 preset

Verified · 88/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The Standel PB-25 is an all-transistor power unit with no tone or volume controls of its own. Its input arrives on a 25-foot cable (with a parallel jack) through a potted input module into a single driver transistor, which feeds a driver transformer and two output transistors in series push-pull into a 4-ohm speaker. A silicon bridge supplies ±25 V rails, and the unit has its own power input and switched power outlet. The factory sheet calls for setting the output for a 1 dB drop at 20 watts.

Tags: american, vintage, bass, solid-state, 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.