Marshall JCM-900 4100 Dual Reverb.

• Separate preamp gain controls: Channel (A) 1-10, Channel (B) 0-20
• Tone network with Treble, Middle, Bass, and Presence controls
• Individual master volume controls for each channel
• Separate reverb controls for each channel
• Manual or footswitch operation for channel selection
• Effects loop with sensitivity control
• Direct and recording compensated line ouputs
• Impedance selection switching
• Two speaker outputs
• High/low power switching (pentode to triode)
• Valve failure LEDs
• Entirely wired and assembled by hand in England
• 100 watt models (model numbers 4100, 4101, 4102) feature 4 x 5881 output valves, 3 x ECC 83 preamp valves
• 50 watt models (model numbers 4500, 4502) feature 2 x 5881 output valves, 3 x ECC 83 preamp valves
• Note: some models came factory equipped with EL34 power tubes instead of 5881s.

Model 4100

• Amplifer head only (requires separate speaker cabinet)
• 100 watts RMS
• Dimensions: 750 (W) x 310 (H) x 220 (D) mm
• Weight: 18.8 kg