What is the “Plexi” Guitar Amp Sound?

You might have heard people describing certain guitar tones as 'Plexi-like', but never been sure what that meant? This article explains what the Plexi is, and how you can achieve that sound on any budget.

James Hurman

James Hurman

When I asked a colleague here at Andertons “what is the Plexi sound?”, he said “Van Halen I” — which brought up an interesting point. I think of the Plexi sound as Hendrix through his Fuzz Face or Clapton on the “Beano” album with John Mayall and The Bluesbreakers. So, what is the Plexi and is there a definitive Plexi sound?

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What is a Plexi?

The Plexi gets its name from the early Marshall amps that used a plexiglass front panel during the ‘60s, before this was replaced by brushed metal in 1969. So really, when we talk about the Plexi, we mean early Marshall amps.

The Birth of Marshall

Jim Marshall was a drummer and London music store owner. The store built a reputation amongst guitarists such as Jimmy Page, Pete Townshend and Ritchie Blackmore, all looking to get their hands on rare Fender amps from across the pond.

In the early ’60s, Fender amps were expensive to import, so in 1962 Marshall decided to start building his own amplifiers to replicate the Fender Tweed Bassman. However, due to the availability of components, he ended up making something that sounded quite different – The JTM45! This was the first Marshall amp, and one of the most iconic. It used KT66 power valves (or tubes, depending on your persuasion) compared to the 6L6 valves of the Bassman, and higher gain ECC83 preamp valves, that the 12AY7s of its American cousin.

These changes resulted in more amp distortion, which became an increasing trend in the early days of British Rock and Roll. These JTM45s got into the hands of Eric Clapton, Jimi Hendrix and Paul Kossoff, and created the famous “British Sound”.

Getting Louder

The Plexi sound is synonymous with incredible volume and crunchy overdrive, as guitarists of the ’60s cranked the volume do achieve more distortion. For me, the quintessential Plexi sound is a JMT45 turned up to 10, as heard from Clapton on the “Beano” album.

During the 1960s, Marshall switched to louder KT88 power valves as his amplifiers got more powerful. Whilst at about 45 watts, the JTM45 was loud, in 1967 he introduced the 50 Watt and 100 Watt Superlead. It’s these 100W Superleads that gave The Who and Jimi Hendrix their sound.

By this point Marshall was using EL34 power valves – these are the ones most commonly associated with Marshall amps. They could produce more volume and gave the amps a stronger mid-range character.

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Hot-Rodded Plexis

As rock music got heavier in the ’70s, guitarists started modifying (commonly known as hot-rodding) their Plexis for more gain – and this is a large part of the reason why the “Plexi sound” means different things to different people. This brings us back to Eddie Van Halen and his hot-rodded Marshall on Van Halen I.

This progression eventually paved the way for the high-gain modern Marshall amps like the JCM800, but the lineage is all routed to those plexiglass front panel amps that Jim Marshall was making in the back of his music store in North West London in the early 1960s. Whether you’re a fan of the classic ‘60s Plexi sound, or the juiced up ‘70s hot-rodded Plexi sound, the aura around the Plexi has etched Marshall into Rock ‘n’ Roll legend.

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Plexi Sound in a Box!

But what if you’re not playing at giant sold out arenas, and you have no use for a 100-watt Plexi? Well you’re in luck. In recent years, pedal builders have looked to capture that distinctive tone in a compact stompbox format, so you can take that sound with you anywhere, at any volume.

From Tone City to Strymon, there’s a Plexi pedal for you. For classic low-to-mid gain Plexi sounds, try the JHS Charlie Brown. Or if you’re looking for the higher gain, hot-rodded Plexi sound, or for a more versatile Plexi pedal, check out the Tone City Golden Plexi, the Universal Audio UAFX Lion 68 Super Lead Amp Simulator Pedal or the Wampler Plexi Mini.

Hear the sounds of the Tone City Golden Plexi 2, or the NUX Plexi Crunch for yourself!

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If you enjoyed this read, check out more of our learn articles!

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James Hurman
James Hurman
James is a member of the Guitar Marketing team and has a particular penchant for vintage gear. He loves Strats, Les Pauls, Fuzz and British amps. He also has an embarrassingly large collection of overdrive pedals on his pedalboard

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