Marshall JCM900 Valve Head

Marshall JCM900 Valve Head

General Specifications

• Amplifier Type: All-Valve (Tube) Guitar Amplifier Head
• Power Output:
  • 100 Watts (4100, MKIII 2100, SL-X 2100)
  • 50 Watts (4500)
• Channels:
  • 2 Channels (Clean & Lead) on Dual Reverb models
  • Single channel with gain switching on MKIII/SL-X
• Construction: Steel chassis with black vinyl covering
• Control Panel: Front-mounted controls

Tube Complement

• Preamp Tubes:
  • 3 × ECC83 / 12AX7 (4100 & 4500)
  • Up to 5 × ECC83 / 12AX7 (SL-X model)
• Power Tubes:
  • 4 × EL34 (most UK models)
  • Some export versions use 5881 tubes

Controls

• Preamp Gain
• Master Volume A & B (model dependent)
• Clean Volume
• Lead Gain
• Bass
• Middle
• Treble
• Presence
• Reverb Level for each channel (Dual Reverb)
• Channel Switching

Rear Panel Features

• Speaker Outputs:
  • 4Ω
  • 8Ω
  • 16Ω
• Effects Loop (Series)
• Footswitch Jack
• Mains Power Input
• HT Fuse & Mains Fuse