Introduction
The Marshall Plexi is one of the most revered and legendary guitar amplifiers ever made. But what exactly is a "Plexi" and where does the name come from?
In short, a Plexi refers to the early Marshall all-valve amplifiers that had a clear Plexiglass front panel. The transparent panel is what gave rise to the "Plexi" nickname. These amps were produced by Marshall starting in the early 1960s up until around 1970, though the Plexi moniker is generally used to describe the non-master volume amps made during that era.
The Plexi amps earned their iconic status due to their unique sound, build quality, high wattages, and association with some of the biggest names in rock history. They deliver an aggressive, bright, and cutting tone that adds bite and attitude to any guitar sound. The distortion is pleasingly raw and dynamic, reacting to the guitar’s volume knob for natural breakup.
Other signature features include the handwired, all-valve circuitry, simple control layouts, and the "wide open" tone enabled by the non-master volume design. These amps oozed rock n’ roll attitude and proved themselves as the amps of choice for countless guitar heroes. The Plexi sound remains coveted to this day.
Origins
The origins of the Marshall Plexi can be traced back to the early 1960s, with the release of the JTM45 in 1962. This 45-watt tube amp was one of the earliest amplifiers to feature the iconic Marshall Plexiglass front panel that gave rise to the "Plexi" nickname.
The JTM45 laid the groundwork, but the Plexi amp as we know it today really arrived in 1965 with the introduction of the 100-watt 1959 Super Lead. This was a breakthrough amp for Marshall, delivering the bright and aggressive distorted tones that would become synonymous with the Marshall sound. Its non-master volume design meant that to push the amp into distortion, you had to crank the volume up loud. This resulted in a very touch-sensitive and dynamic overdrive with rich harmonic content.
After the success of the Super Lead 1959, Marshall transitioned to using 1959 and 1987 nomenclature for their model numbers in the late 1960s, moving away from the JTM prefix. But the key DNA of the Plexi – the all-valve circuit, iconic Plexiglass panel, and signature sound – remained intact throughout its evolution from those earliest JTM amps.
Anatomy of a Plexi
The anatomy of a Marshall Plexi amp is what gives it such an iconic look, feel, and tone. Let’s examine some of the key components that make a Plexi a Plexi.
The most obvious distinguishing feature is the Plexiglass front panel. Early Plexis used actual Plexiglass panels, which gave the amps their nickname. The transparent panel showcases the inner workings while providing protection. Later Plexis transitioned to metal panels, but retained the classic Plexi style.
Inside, Plexis utilize an all-tube circuit design. Unlike some amps that incorporate transistors or solid state components, Plexis are purely valve-driven. Preamp stages use smaller tubes while the power amp section houses larger output tubes. This all-tube design contributes greatly to the Plexi’s natural overdrive and harmonically rich tone.
Another hallmark is the handwired circuitry. Instead of printed circuit boards, Plexis are hand wired in a point-to-point fashion. This labor-intensive build process allows greater customization and fine-tuning of the signal path. Many players feel handwired amps have a more organic, musical response.
The Plexi anatomy combines iconic cosmetics with carefully crafted circuit design, creating an amp that looks, feels, and sounds like no other. These unique characteristics have cemented its status as one of the most influential guitar amps ever made.
The Plexi Sound
The Marshall Plexi amps are renowned for their iconic, aggressive guitar tone that helped define rock music. The sound of a cranked Plexi is nothing short of legendary.
A key factor in the Plexi sound is the bright, cutting treble response. The Plexi is known for having a very lively, detailed top end that adds bite and definition to the distortion. This signature treble boost allows Plexi tones to cut through a mix clearly.
The Plexi’s non-master volume design also plays a big role in the sound, as it allows the amp to be cranked up to induce natural tube overdrive. Pushing the volume brings out the Plexi’s singing sustain and rich harmonic overtones. Going beyond the sweet spot causes the amp to compress in a very musical way, yielding vocal-like lead tones.
To dial in those cranked up Plexi tones, guitarists typically set the Normal volume high, around 8 or above. The Tone controls can then shape the EQ – Treble for bite and Presence for added top end sizzle. Many rock guitar gods found their signature sound this way, by simply winding up the Plexi’s volume knob.
The Plexi’s wide range of distortion, from bluesy grit to molten roar, cemented its status as an amp capable of some of the most coveted electric guitar tones ever produced. From Eric Clapton to Slash, countless icons have used the Plexi as their tonal Holy Grail.
Models and Variations
The Marshall Plexi amps came in a variety of models and configurations over the years. Some of the most iconic and sought-after models include:
1959 Super Lead
The 1959 Super Lead 100-watt head is considered by many to be the quintessential Plexi amp. With its bright and aggressive high-gain tone, this amp defined rock guitar sounds in the late 60s and 70s. Versions were produced both before and after the addition of master volume controls in 1967.
1987 Lead
Following the success of the 1959 Super Lead, Marshall introduced the 50-watt 1987 Lead head in 1965. It had a similar circuit design but lower wattage, making it more practical for smaller venues. The 1987 Lead went through the same transition to a master volume version.
JTM45
The very first Plexi amp was the JTM45, released in 1962. The JTM45 laid the foundation for Marshall’s signature sound. Though lower in wattage, it had that same rich overdriven Plexi tone.
Combo Versions
In addition to heads, many Plexi models were produced as combo amps with built-in speakers. Popular combos included the 1987 Lead Combo and 50-watt 1959SLP combo.
Custom Modifications
Plexi amps are often hot-rodded with mods like added gain stages, different tone stacks, increased wattage, or upgraded speakers. Boutique amp builders offer custom Plexi clones with modern tweaks and refinements.
So whether it’s a stock ’68 Super Lead or a souped-up custom Plexi, there are many options for getting those iconic Marshall tones. Both vintage and reissue Plexi heads and combos are highly sought-after by tonehounds.
Famous Plexi Users
The Marshall Plexi reached iconic status in large part thanks to the legendary guitarists who used them. During the 1960s and 70s, many of the biggest names in rock depended on their Marshall Plexis to achieve their signature sounds.
Jimi Hendrix was one of the earliest Plexi adopters. His use of Marshall stacks with Plexi heads at high volumes contributed greatly to his pioneering distorted and feedback-laden guitar tones. Hendrix often spoke of his love for the Marshall crunch and sustain.
Eric Clapton first discovered the Marshall tone when he plugged into a JTM45 Plexi during the recording of John Mayall’s Blues Breakers album in 1966. Clapton’s lush lead tones on that record became known as the "woman tone" and launched Marshall into rock stardom.
Pete Townshend of The Who frequently used Marshall Plexis throughout the 60s and 70s both live and in the studio. The Plexi’s aggressive high-end was crucial in achieving Townshend’s trademark windmilling power chords and feedback.
Jimmy Page famously used Marshall SLP 1959 and 1987 Plexi models to record most of Led Zeppelin’s studio albums. From crunchy riffs to violin-like leads, Page’s Plexi was the driving force behind his influential guitar work.
Ritchie Blackmore of Deep Purple counted on Marshall Plexis to pioneer the use of distortion and aggressive rock riffs on songs like "Smoke on the Water." Blackmore once said of the Plexi tone: "It seemed to scream at you."
From rock to blues to metal, countless guitar greats like Jeff Beck, Angus Young, Slash, and more used Marshall Plexis to help take their playing to legendary status. The Plexi’s unique responsiveness and dynamic overdrive made it the amp of choice for shaping iconic guitar tones.
Legacy
The iconic Marshall Plexi amps continue to inspire guitarists and amp builders today. Modern amp companies frequently release updated takes on the classic Plexi design and sound.
Modern Plexi-Inspired Amps
Many amp manufacturers now offer their own versions of Plexi-style amps. These amps aim to capture the vintage Marshall tone using modern components and features like added gain channels and reverb. Popular modern Plexi-style amps include:
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Marshall Astoria Series: Marshall’s modern take on the Plexi sound, featuring EL34 tubes and a dynamic clean channel.
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Friedman Small Box: Designed to emulate the Plexi’s signature distortion tones at lower volumes.
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Orange OR120: A 120-watt Plexi-inspired head loaded with 4 EL34 power tubes.
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Fender ’65 Twin Reverb: Models the preamp of a late 60s Marshall Plexi amp.
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Vox AC30HW60: Vox’s hand-wired Plexi emulation, with EF86 preamp tubes.
Affordable Plexi-Style Alternatives
While original vintage Plexis are scarce and expensive, there are more affordable alternatives for getting those classic British tones on a budget:
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Egnater Tweaker: An all-tube amp with a "Plexi" voicing switch to dial in Marshall flavors.
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Peavey Classic Series: Peavey’s take on vintage Marshall tones, at a fraction of the price.
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Bugera V55: An inexpensive Plexi-inspired amp using modern components.
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Marshall Origin Series: Marshall’s budget-friendly line with a 20-watt Plexi voicing.
Digital Plexi Profiling Amps
With amp modeling technology, it’s now possible to digitally profile the sound of a Plexi amp. Products like the Kemper Profiler, Fractal Axe-Fx, and Line 6 Helix all contain profiles that emulate the Plexi’s tone. Some amp sim plugins like Softube Marshall Plexi also capture the Plexi sound for recording direct. While not identical to the real thing, these tools make Plexi tones more accessible than ever.
The Plexi’s influence persists through both analog and digital domains. While the original amps hold mythical status, the Plexi’s signature sound continues to inspire new generations of players through modern reinterpretations.
Notable Recordings
The Marshall Plexi has been featured on countless iconic albums and songs over the decades. Many legendary artists insisted on having the Plexi be part of their studio setup to capture its distinctive tone on record.
In the studio, Jimi Hendrix relied heavily on his Marshall Plexis to record albums like Are You Experienced and Electric Ladyland. The Plexi’s bright and aggressive distortion was an integral part of his groundbreaking guitar sounds. Songs like "Purple Haze" and "Voodoo Child" simply wouldn’t have the same tone without Hendrix’s cranked up Plexis.
Jimmy Page also made extensive use of Marshall Plexis when recording Led Zeppelin’s early albums at Olympic Studios. The band’s 1969 self-titled debut album highlights Page’s Plexi tones throughout, especially on crunchy riffs in "Good Times Bad Times" and "Communication Breakdown." Page continued using Plexis in the studio through Led Zeppelin IV in 1971.
Other groups like The Who, Queen, Aerosmith, and Van Halen all recorded with Marshall Plexis to get their signature sounds down on tape. Albums like Who’s Next, A Night at the Opera, Toys in the Attic, and Van Halen I all relied on the Plexi’s natural overdrive and rich harmonics coming through speakers.
Live on stage, bands would push their Plexis to the limit to achieve roaring distorted tones. Jimi Hendrix’s live versions of "Foxey Lady" and "Voodoo Child" at Monterey Pop and Woodstock were delivered through cranked 100-watt Marshall stacks. Queen’s Brian May also used towering walls of Plexi amps to get his singing lead tones that were just as vital to Queen’s live sound as Freddie Mercury’s voice.
The Marshall Plexi’s role in these iconic recordings and performances cemented its status as an indispensable tool for achieving some of the greatest guitar tones in rock history.
Collectibility
The vintage Marshall Plexi amps, especially from the 1960s, are highly sought after by collectors and guitarists. Their rarity, iconic status, and legendary tone make original Plexis extremely valuable.
The holy grail Plexis are the JTM45 and 1959SLP models from the mid-1960s. Since only a few thousand of these were ever produced, mint condition examples can easily fetch over $10,000 at auction. Even non-working vintage Plexis can sell for several thousand dollars due to their collectibility.
Other factors that determine the value of a vintage Plexi include condition, whether it’s been modified, matching serial numbers on the chassis and speakers, and inclusion of the original footswitch. Completely unmodified examples in excellent cosmetic and working condition with matching serial numbers will always command the highest prices.
Later Plexi reissues from the 1990s and 2000s are also collectible, though not nearly as valuable as the original 1960s amps. Still, limited edition reissue Plexis like the 1987x can sell for upwards of $3,000.
For guitarists and collectors, owning a vintage Marshall Plexi represents the holy grail. These amps defined the sound of rock and still represent the pinnacle of guitar tone. Their legendary status ensures original Plexis will likely only continue to appreciate in value.
Conclusion
The Marshall Plexi amps represent a legendary era in guitar amplification history. With their iconic Plexiglas front panels and all-valve circuitry, the Plexi amps like the 1959 Super Lead and JTM45 pioneered the British rock and blues tone that would dominate the 60s and 70s.
The Plexi sound – with its bright, aggressive crunch and singing lead tones – became the quintessential rock guitar tone, shaping the signature sounds of guitar gods like Jimi Hendrix, Eric Clapton, and Pete Townshend. Though the Plexi amps were eventually phased out in favor of master volume models, their influence continued through Marshall’s subsequent amp designs as well as the many boutique amp builders who have resurrected the Plexi style.
Even in today’s digital modeling era, original vintage Plexi amps remain highly sought after and command premium prices on the collector market. More than just vintage amps, they represent the holy grail of guitar tone – an aggressive, in-your-face attitude that modern amp designers still try to capture. The Plexi’s rawness and simplicity gave it an organic, almost living quality that guitarists have been chasing ever since. For these reasons, the Marshall Plexi amps will forever be remembered as some of the most important and iconic guitar amps ever created. Their legendary tone lives on today as guitarists continue to celebrate these amplifiers that defined rock n’ roll.