Airline GDR-8503A / GDR-8504A - Channel B preset

Verified · 85/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The Airline GDR-8503A and GDR-8504A are early-to-mid 1960s budget tube combos from Montgomery Ward's Airline brand, manufactured by Valco with the typically warm, slightly rough tone that characterizes Valco-built instruments. The GDR designation identifies these as models from the reverb-equipped segment of the Airline line, offering built-in spring reverb for added ambience. These amps represent the economy end of American amplification with a raw, characterful voice that has attracted blues and garage rock players.

Tags: american, vintage.

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.