Marshall JCM900 Dual Reverb 4100 preset

Verified · 89/100 confidence. Complete schematic. All component values readable. Parameters derived directly from the circuit.

The JCM900 4100 Dual Reverb is a 100-watt two-channel head with independent reverb levels per channel, two master volumes and a series effects loop. Its gain channel uses diode clipping plus a boost switch to reach higher gain than the JCM800. It was the more popular of the two main JCM900 heads, with a brighter, more scooped voice and less low-end growl than a JCM800.

• Years produced: 1990–1999
• Made in: UK
• Wattage: 100W
• Channels: 2
• Preamp tubes: 3× ECC83
• Power tubes: 4× EL34

Known for: John 5, Neil Giraldo.

Tags: british, crunch, high-gain, reverb, el34, high-wattage, 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.