Gear Review: Marshall JCM 900 Mk III 2100

In a time where modern rock was once again at the cusp of an overture, a new decade prompted a new series of flagship 100 watt JCM head and combo amplifiers from Jim Marshall. The first eighteen months of productions gave birth to the mark-three high gain master volume models. These were primarily based on the previous JCM 800s with three 12Ax7 pre-amp tubes and four EL34 power amp tubes— the most significant upgrade being the ability to control the gain of the pre-amp and power stages independently.

The 2100 model features a switchable half power mode (50 watts), an effects loop between the pre-amp and power stage, two independent channels with separate volume controls (foot switchable), direct output, recording compensated output, and a presence control along with the standard marshall three band EQ. Also, two speaker outputs are available in 4, 8, and 16 ohms. 

These babies have just as much punch as a classic JCM 800, but with a slightly darker tone and a higher overall gain. Not to say you couldn’t crank out sounds ranging from seventies plexi to nineties alternative and metal— all Marshall gems definitely have the balls. The minimal tonal downside is the darkness; if an 800 series tone is what you’re after then a graphic EQ brightening up the effects loop will do the trick. Also, this specific model has the tendency to blow out their power transformers after a couple decades, so beware about replacing it when obtaining one.

After 1992 the Hi-Gain Master Volume JCM 900 was no longer produced, and the rest of the series line turned into what they’re primarily known for— muddy duds. The change to 5881/6L6 tubes and Reverb was a decision made to follow the Nu-Metal trend, and are considered to be nothing special in the realm of Marshall history. Re-writing the bad name of the series, Marshall re-issued the JCM 900 in a new model (SLX 4100) which was a reproduction of the 2100 with the kinks ironed out, and an extra 12Ax7… the combination of the SLX re-issue and the more common later variants significantly lowered the price for vintage 2100 heads. Uncommon at best, searching for one of these lost gems isn’t too difficult a task and can get you the classic JCM 800 sound with all of the balls, and a fraction of the price ( around $500-$600 ).

The Marshall JCM 900 Mk III 2100 is definitely off the beaten track, and somewhat of a cult classic among its aficionados. The Master Volume, switchable power modes, and price make it easily obtainable and incredibly versatile.