JCM-800 Pre-amp simulator

Project overview

The JCM 800 pre-amp emulates the tone of the classic Marshall’s JCM 800, using the same circuit schematic that you will find in the most famous British Amps from the ’80s, using JFET transistors instead of vacuum tubes. Try this board and put the intense tone of their JCM 800 amplifier into your

pedalboard. This is a wide-ranging, British-flavored overdrive that can be pushed well into the high-gain territory.

Introduction

This circuit has been developed to recreate all the gain and tone from the famous Marshall’s JCM 800 Pre-amps, replacing the vacuum tubes for the JFET J201. This design’s origin goes back to 2004 by a schematic published by Electric, following the same conversion style as the ROG designs as the Azabache, Britania, Thunderbird, etc.

This version includes five trimmers to bias the JFET according to your taste. It also features pads to use standard through-hole J201 or the more available and reliable SMD version.

• Powered by six J201.
• Five Internal Trimpot to regulate bias of the transistors.
• Designed to use onboard potentiometers. Keep it tidy without using cables!
• The compact format fits perfectly in a 125B enclosure

Controls

• Bass: Tonefor the bass frequencies.
• Mids: Tone for the mids frequencies.
• Treble: Tone for the treble frequencies
• Master: Controls the output gain of the preamp.
• Level: Controls the output volume
• Gain: Controls the preamp gain

For any technical questions regarding this build don’t forget to check out our Facebook Group and our forum at Free Stomp Boxes.

JCM 800 Emulator V2.1 – Building Docs

JCM 800 Emulator V2.0  – Building Docs

JCM 800 Emulator V1.0 – Building Docs

JCM 800 – Drilling Template