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

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

The Airline GDR-8503A and GDR-8504A are two-channel Montgomery Ward tube amps with a remote preamp control panel. Channels A and B each have three inputs, a 12AX7 triode and their own Volume and Tone. In the main chassis a second 12AX7 provides a gain stage and a split-load phase inverter for two cathode-biased 6V6GTs, while a 6AU6 oscillator supplies vibrato with Strength, Speed and a footswitch. A 6X5GT rectifies the supply.

• Made in: USA
• Wattage: 14W
• Channels: 2
• Preamp tubes: 2× 12AX7, 1× 6AU6
• Power tubes: 2× 6V6GT

Tags: american, vintage, 6v6, vibrato, two-channel, low-wattage.

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.