Following in the footsteps of the JCM800—Marshall’s best-selling model of all time—this model emerged as the face of Marshall in the 1990s. It was adopted by many studios and live music venues, and is still actively in use today. In recent years, it has become even more widespread than the JCM800, so many of you have likely had the chance to try it out.
While this model pioneered “modern Marshall” and, by extension, modern high-gain amplifiers, it’s also the one that has drawn skepticism from longtime Marshall fans, who often remark, “Well, these modern Marshalls…”
However, when you experience it again today, you’ll reaffirm that it’s a model brimming with many appealing qualities: its cutting-edge sound, ease of use, durability, and value for money. Of course, its sharp drive edge—which can more than hold its own against recent high-gain models—is a powerful characteristic that leaves a distinct impression. This truly speaks to its track record as the enduring “face” of Marshall from the ’90s onward.
Background
The JCM900 was unveiled at the NAMM Show in January 1990. Taking the baton from the JCM800—which had achieved record-breaking sales worldwide throughout the 1980s—it was given this name with the intention of becoming the defining amplifier of the 1990s.This coincided with the heyday of hard rock and heavy metal—a genre seeking sounds even harder than hard rock. It was also the year Metallica made their Grammy Awards debut. Everyone in that scene had grown tired of the gain offered by existing amplifiers and was seeking models with even higher gain.
Although Marshall had achieved global success with the JCM800 up to that point, by the late 1980s, many players were no longer satisfied with the standard gain settings of the JCM800.As I’ve mentioned before, this sparked a movement to modify Marshalls, which gave rise to many talented amp builders such as Reinhold Bogner and Mike Soldano. On the other hand, not everyone possessed such advanced technical skills, and the market began to be flooded with poorly modified Marshalls.Some of these modifications caused noise to increase along with the gain, produced terrible sound, or even shortened the amp’s lifespan.Amid this situation, Jim Marshall—having realized the need for high-gain models—first announced the Jubilee series in 1987 to mark Marshall’s 25th anniversary. Described at the time as “the most distorted Marshall,” it was well-received by top artists of the era, such as Richie Sambora of Bon Jovi and Slash of Guns N’ Roses.Although the Jubilee series was intended to be a one-year, limited-edition model for the 25th anniversary, production continued until 1989 due to the overwhelming demand at the time. Then, as the 1990s approached, Marshall unveiled a high-gain amp it had redesigned to represent the sound of a new era—the JCM900. Moreover, plans were already in the works for a 30th-anniversary model to follow the Jubilee.
So, which JCM900 is right for you?
Like the JCM800, the 900 came in many variations. However, they can be broadly divided into two main categories: the High Gain Dual Reverb (roughly speaking, a 2-channel model) and the High Gain Master Volume (roughly speaking, a 1-channel model). Each was available in 50W and 100W versions, as well as head and combo configurations.
As the name suggests, the High Gain Dual Reverb model features two gain channels and two master volume controls that can be switched via a footswitch, with reverb settings adjustable for each channel. This means you can switch between clean and overdrive tones; for example, you could set the clean channel to have deeper reverb while the overdrive channel has shallower reverb (or none at all). This model is highly versatile and was the most widely adopted for professional use.This is generally the model you’ll see in practice studios.
The High Gain Master Volume model also features two gain settings and two master volume controls, but only the master volume can be switched via the footswitch. While this allows for a big, “BOOM!” sound during solos, it cannot be used to switch between clean and drive modes. Once you’ve dialed in the distortion, it stays that way; if you want a clean sound, you’ll have to adjust the gain setting.(However, this “solo mode”-style master switch is actually quite modern by today’s standards and is featured in recent models like the Koch.) The two gain controls are two-stage gain settings that affect a single channel simultaneously, making it possible to create some pretty heavy distortion. In short, you could call it a dedicated distortion pedal.
Let’s crank up the distortion~? The gain dial goes all the way up to 20!
Features common to both models include an effects loop with level control, a direct output, a Hi/Lo switch to toggle between 3-pin and 5-pin modes, and the OUTPUT VALVE FUSE—a power tube protection circuit introduced for the first time. In the event of a problem with any of the tubes, this fuse blows on the normally functioning tube to prevent overload and protect the other tubes from damage.
How to Read the Model Number
XXXX (4-digit number)
4th digit: Indicates the model. 4 = High Gain Dual Reverb / 2 = High Gain Master Volume
3rd digit: Indicates the power output. 1 = 100W / 5 = 50W
1st digit: Indicates the number of speakers. 0 = 0 speakers (head).
Example: 4102—4 = High Gain Dual Reverb, 1 = 100W, 2 = 2 speakers. This indicates a combo amp with channel switching, 100W, and 2 speakers.
What is “SLX”?
Models with “SLX” in their names, such as the 2100SLX and 2500SLX, are also commonly seen. How do these differ from the standard 2100 and 2500 models?
In 1991, the year after the JCM900 was announced, two “monster amps” appeared in the U.S. that would go on to define the scene: the Mesa/Boogie Dual Rectifier and the Peavey 5150. These two landmark high-gain amplifiers, which arguably changed the course of history, were released simultaneously that year.It’s unclear whether Marshall was feeling the pressure from this, but in 1993—whether as a countermeasure or to compete in the high-gain arena—they added an additional preamp tube to the preamp stage of their existing High Gain Master Volume models. With two additional amplification stages, the amp was now configured for even higher gain. It was then labeled “SLX,” standing for “Super Lead X-tra Gain,” further solidifying its reputation as a heavy-drive machine.
Previous models had three preamp tubes
The SLX now featured four preamp tubes!
Around the same time, the power tubes used in all Marshall models were changed from EL34s to 5881s. While this is said to have been due to a shortage of stable supplies from Sovtec—the Russian tube manufacturer Marshall primarily used at the time—this change resulted in an even clearer, more solid, “crisp” tone, which went on to become the signature sound of Marshall in the 1990s.This configuration continued until 1998, when Marshall began using tubes from Svetlana, another Russian tube manufacturer; after 1998, most models reverted to the EL34 configuration.
EL34 and 5881
As mentioned above, starting around 1993, the power tubes in most Marshall tube amplifier models were switched from EL34 to 5881.Not only the JCM900, but also the vintage reissues—the 1959SLP and 1987X—began using the 5881, and it is true that this caused disappointment among some die-hard fans. There is a sense that the negative phrase “These days, Marshall…” originated during this period.
In terms of sound characteristics, the 5881 is known as a highly reliable 6L6 tube. It produces a relatively clean tone with minimal distortion, remains fairly mild even at low volumes, and does not undergo drastic sound changes even when the volume is cranked up. For this reason, it is well-suited for dry clean sounds and solid distortion tones, and historically, it has been a familiar tube in Fender amplifiers such as the Bassman.It is also used in many Mesa/Boogie models and the Peavey 5150, so it can be said to be a tube that epitomizes the American sound.
On the other hand, the EL34 has a sharp, biting tone at low volumes, but as the volume increases and it begins to clip, the tone changes dramatically, transforming into a thick, sticky sound with a midrange emphasis.In addition to being a tube that colored some of the most glorious chapters in Marshall’s history, it was also used by leading British amp manufacturers such as Hiwatt and Orange, which led to a near-mythical belief—particularly in Japan—that “the British sound is the EL34.”
Given that this change to the 5881 came on the heels of such a legacy, I can certainly understand why particularly avid British rock fans raised critical voices. I also remember feeling a bit disappointed at the time that only vintage reissues with the 5881 configuration were available.It was more of a sentimental feeling than anything to do with the sound itself. Fortunately, however—or perhaps it’s just a matter of perspective—EL34 tubes made a comeback in almost all models released from 1998 onward, and not only the Vintage Series but also the JCM900 returned to the EL34 configuration. This tradition has continued ever since the JCM2000 and remains in place today.
Maybe it’s just because I’m living in this era now, but when I see a JCM900 with 5881 tubes, I actually feel a bit nostalgic.The characteristic qualities of a high-gain amp are actually emphasized more, and in a way, it even sounds like “a more authentic JCM900 sound.” This is a slight digression, but even the 5881-equipped 1959 SLP, when I listen to it again now, has its own charm. It’s almost amusing to think back on how disappointed I was by it back then.
That’s one of the interesting things about the JCM900—there are versions with both 5881 and EL34 tubes. The early models (up to around 1993) and the more recent ones (from the second half of 1998 onward) use EL34s, while the models in between use 5881s. If you spot one in a studio or somewhere else, wondering, “Which version is this?” might be one of the joys of the JCM900.
Models from the 5881 era have a label on the top indicating that they use 5881 tubes.
The JCM900 Family?
The 6100 30th Anniversary Model, which was apparently developed at the same time
Although not part of the JCM900 series, this model has a deep connection to the JCM900 and should not be overlooked: the 6100, with its striking blue leather finish. It was Marshall’s first three-channel amp, featuring Clean, Crunch, and Lead channels. Equipped with MIDI, it was a pioneering model that led the way globally.It was released about two years after the JCM900, in 1992—the 30th anniversary of Marshall’s founding. While three channels seem commonplace today, it was groundbreaking at the time.
In fact, it’s said that the development of this model took place almost simultaneously with that of the JCM900.However, perhaps because it was difficult to produce it alongside the various JCM900 models during the global release of the JCM900 series, it was reportedly held back until the anniversary year of 1992. As mentioned earlier, this was right in the midst of the high-gain boom. It’s possible that Marshall also intended to gauge the moves of other brands following the release of the JCM900.
The 6100 debuted amid these trends as a fully independent three-channel amp, making it one of the earliest three-channel models produced worldwide. Channel 1 is a clean channel with two modes: a classic Marshall-style clean tone and a Fender-inspired clean tone, selectable via the Mid Shift and Bright controls.Channel 2 is what could be called the rhythm channel, offering a choice between a vintage sound reminiscent of the JTM45, a sound typical of the JCM800—which had been the standard up to that point—and a JCM900-style sound. Furthermore, Channel 3 delivers a high-gain sound unlike anything heard before—arguably the most powerful in Marshall’s history. It is believed that this sound not only drove the evolution of the JCM900 but also served as the foundation for the aforementioned SLX.Covering everything from traditional tones to cutting-edge sounds, the 6100 amazed and won the hearts of many musicians. Known for being used by Joe Satriani and Gary Moore, it became affectionately known as the “Blue Marshall.”
The first limited-edition anniversary batch was fully gold-plated—a true testament to attention to detail, with even the tube covers and tube springs finished in gold, not just the chassis.A gold panel was also used for the front logo on the cabinet. Only 500 units (800 combo units) of this model were produced worldwide, and it is known as the 6100LE. After that, models with the standard chassis—except for those with blue leather—were produced until the end of the anniversary year, and from the following year onward, models with black leather were produced until the late 1990s.
Rediscovering the Appeal of the JCM900
In 1999, as the 20th century drew to a close, the JCM2000 series was released as a new model designed with the 21st century in mind. The JCM2000, which even today is considered a flagship model, captivated everyone from young players to veterans of yesteryear, and it seemed as though the era of the JCM900 had come to an end.Indeed, as the JCM2000 gained popularity, many JCM900 models—such as the SLX—gradually disappeared from the market. However, the High Gain Dual Reverb Series 4100, one of the most iconic models in the JCM900 lineup, is still in production today. Since its debut in 1990, it has endured the turn of the century for 18 years without any changes to its specifications. Given the diverse changes in the music scene over that time, this can certainly be called an exceptionally long-running product.According to Marshall’s official statement, the reason for this is that “the sound is absolutely thick and possesses vintage DNA”—and there’s certainly no exaggeration in that description. While countless “distortion” amplifiers have appeared since then, the JCM900 delivers a tone that feels like natural drive seamlessly transitioning into high gain. In a sense, the JCM900’s defining characteristic might be that it is the world’s “hardest” overdrive amplifier.
I’d also add that its simplicity, ease of use, and the intuitive feel you get when you first pick it up are major attractions. Furthermore, it doesn’t generate excessive heat, and even after using it for long periods once you’ve dialed in your sound, the tone remains stable—and it’s rarely prone to malfunctions. I believe these factors are why it has earned the trust of so many sound engineers. If I may add my personal opinion, it’s the most reliable model when used with a rack-mounted preamp and connected via the return.I feel that as long as the JCM900 is in the mix, you can rest assured.
The JCM900 boasts this level of reliability. While it’s by no means a pure vintage sound, nor is it a wildly modern heavy-gain amp, there’s no doubt that it has been a behind-the-scenes powerhouse, steadily supporting the scene for nearly 20 years. “Simple,” “tough,” “hard”… all the words essential to rock music are embodied in the JCM900. I can’t help but feel that way.
