Valco National 1205 - Instrument preset

Verified · 90/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The National 1205 (Valco chassis 510-4) is a 1940s Valco-built public-address style amplifier also used for instruments. A high-impedance mic input and two instrument inputs each get their own 6SJ7 pentode and 500k volume control, mixing into a 6SN7 gain stage and a tone control, then a second 6SN7 as phase inverter driving a push-pull pair of 6L6s. A 5Y3GT rectifier supplies the high voltage and the speaker has a 1000-ohm field coil.

Tags: american, vintage, 6l6, 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.