Marshall JCM 900 Model 4100

SL-X Extra Strength -50 Watt 2500 SL-X and 100 Watt 2100 SL-X amplifier formats. Extra ECC83 [12AX7] valve in the pre-amp-Switchable master volumes -4 band EQ-Pre-amp volume control and a Gain sensitivity [which goes from 0-20!] Direct-Effects loop-output-Switchable high and low output-Valve failure LEDs. Dual Reverb Flexibility-A wide variety of head and combo formats-Two independent channels-Independent Gain and Volume controls -Treble, Middle, Bass and Presence controls tone reverb level controls for each channel-Series Effects loop-Compensated Line Out High to Low power switch [100 Watts down to 50 Watts on 100 Watt models and 50 Watts down to 25 Watts on 50 Watt models]-Valve failure LEDs.-Unique fail-safe circuit on 100 Watt models to keep the amp running in the event of a valve failure to get you through to the end of the gig.