Marshall JTM45 Offset Reissue (JTM45OS) - Normal preset

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

A limited Marshall reissue of the earliest offset-chassis JTM45, from 1999. Normal and High Treble channels, each with two inputs and its own volume, feed a cascaded ECC83 gain stage and cathode follower driving Treble, Middle and Bass, then an ECC83 long-tail inverter with Presence. Two KT66s run off a GZ34 valve rectifier and choke for a rated 30 watts RMS into 4, 8 or 16 ohms, giving warm, sagging early-Marshall crunch.

• Made in: UK
• Wattage: 30W
• Channels: 2
• Preamp tubes: 3× ECC83
• Power tubes: 2× KT66

Tags: british, reissue, vintage, kt66, crunch, two-channel, mid-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.