Arming the Artists

What is a 'Plexi'?

Posted: 15th June 2023

‘Plexi’ – we’ve all heard the name, but what does it mean and what is a ‘Plexi’ amp? In this article, we dive into the history behind the term, what the classic ‘Plexi’ sound is and why people still want to play ‘Plexi’s’ today.

Read time: 3 mins

The term ‘Plexi’ came from the word plexiglass - a type of acrylic that was produced by American manufacturer Plexiglas, whose brand name became synonymous with their product. An easy way you can distinguish between ‘Plexi’ and non-‘Plexi’ amps, is by their aesthetic, the gold ‘Plexi’ panel on these amps looks like a letterbox slot.

It’s important to note that all Marshall ‘Plexi’s’ are non-master volume amplifiers. This means each channel has its own volume control, whereas master volume amps also have one master volume knob that controls all channels as well as being a pre-amp gain volume knob. Master volume amps allow players to dial in their desired distortion, while still being able to keep the overall volume of their amp low. With a non-master volume amp, you can achieve varying levels of distortion depending on the overall volume, with clean tones at low volume and increasingly distorted tones as you get louder. Many people consider using non-master volume amps to be a pure way of playing guitar – you get out what you put in due to the raw relationship between tone and volume.

JTM45

The first ‘Plexi’ amp we produced was the JTM45 - this iconic 30-watt head is what started it all. Based on a Fender Bassman with changes to valves and an all-aluminium chassis, the original valves were later replaced with EL34’s that gave the amp significant power and created the Marshall legacy. While many people don’t consider the JTM a ‘Plexi’ amp, cranked to 10 it produces iconic crunchy overdriven ‘Plexi’ tones. This is because the RMS-rated wattage of the JTM is 45-watts, which is the true power the amp is capable of handling and is most notably heard on the ‘Beano’ album by Blues Breakers with Eric Clapton. Find out more about the JTM 45 here.

1959

The amp most associated with being a ‘Plexi’ is the legendary 100-watt Super Lead 1959, which in association with its matching 4x12 cab, gave rise to the ‘Marshall Stack’. The 1959 was first introduced in 1965 after The Who’s Pete Townshend asked us to create an amp with even more power. It was originally built with four KT66 valves, three ECC83 preamp valves and later four EL34 valves to produce the iconic Marshall roar. It was clear that the sonic range of the 1959 was different and like nothing we had produced before. Due to its power, tone, and sheer volume, the 1959’s popularity skyrocketed to new heights and became the amp of choice for many guitarists including Jimi Hendrix, Angus Young and Jimmy Page. The 1959 being seen and heard on some of the biggest stages in the world, marked the desirable ‘Plexi sound’ as the sound of rock.

The peak of the ‘Plexi’ era was from 1962 until mid-1969 when we switched to using brushed aluminium panels. Despite this, we still produce the much-loved ‘Plexi’ amps today. The popularity and heritage of the 1959 have stood the test of time, which is why in 2005, we unveiled the 1959HW. The 1959HW is a faithful reissue of the original definitive ‘Plexi’, only this time, it has been hand-wired by our meticulous engineers. Like the original 1959, the 1959HW is not for the fainthearted and delivers that classic Marshall tone with the same overdrive and crunch. The 1959HW has been used by many guitarists including Dan Hawkins and Bernie Marsden, who even had his own limited edition white faux snakeskin signature reissue. The louder you play the 1959HW, the better it sounds.

Listen to our iconic 'Plexi' amps

We plugged into some of our most iconic ‘Plexi’ amps – the JTM45, 1987X AND 1959HW, and using the same cab, we compared their clean and dirty tones so you can hear them for yourself.