For a British-built Marshall, the Studio JTM ST20H is fairly priced and we reckon it’s good value for money compared to the competition, offering classic tones and cool vintage looks to match.
Pros
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Compact and portable.
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Nearly as loud as the JTM45 and doesn’t sacrifice any tone. Great for classic Brit blues/rock when cranked.
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Ideal pedal platform when clean.
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Useful series loop.
Cons
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Non-master volume design means you have to crank it up. Speaker has to stay connected when DI recording.
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No remote footswitching option.
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While there will always be a place for the traditional 100-watt head and 4x12 stack, those places have become more scarce in recent years.
At the professional end of the market, advances in digital modelling, PA systems and in-ear monitoring have made it possible for guitarists to leave their treasured tube amps at home and take advantage of the reliability and convenience of digital solutions – although for many players the sound and feel of valves remains an essential part of their rig.
For those who want the proper valve Marshall experience in a more compact and neighbour-friendly package, the company’s Studio amplifiers have proved to be a popular choice. Now there’s a new and long-anticipated addition to the range: the Studio JTM.
Like Marshall’s other Studio amplifiers, the Studio JTM is a lower-powered and more portable version of a full-sized classic Marshall amp head, in this case the original Hanwell-manufactured JTM45 MkII, which was largely responsible for shaping the sounds of the mid-’60s British blues-rock movement and everything that followed.
(Image credit: Future / Phil Barker)
The cosmetics are spot on, featuring a silver control panel, non-offset black and fawn vinyl-covered plywood sleeve, thin dark gold piping and a reproduction of the ‘coffin badge’ nameplate (so-called because it was sourced from a funeral casket hardware supplier), used on early products made prior to 1965.
Inside the steel chassis, most of the JTM’s electronics sit on a large high-quality printed circuit board, including the bases for its three 12AX7s and two 5881 power valves. Smaller boards support the front- and rear-panel components, with neat wiring and Molex connectors joining everything together. Most of the weight saving comes from smaller transformers, which are around half the size of the higher-powered originals.
(Image credit: Future / Phil Barker)
The JTM’s front panel features include two pairs of high- and low-gain input jack sockets feeding separate Normal and High Treble Loudness controls, and a shared EQ with knobs for Presence, Bass, Middle and Treble.
The preamp channels are permanently on and can’t be footswitched, but they can be jumpered using a short patch lead to connect the jack sockets.
In this mode, both volume knobs are active and act as the amp’s primary tone controls, besides adding a little more gain. The Standby switch is now a three-way affair, delivering a full 20 watts of power in the High position and a more manageable five watts in the Low position, with standby in the centre.
(Image credit: Future / Phil Barker)
Around the back there are a few modern extras, including a series effects loop with a Bypass switch and a speaker-emulated line out. There’s also a full complement of speaker output jacks to handle 16, eight and four-ohm loads.
While the Studio JTM looks authentically vintage, under the skin it’s a typical modern Marshall product, built to a very high standard and more than capable of handling pro touring use. The early cosmetic styling may not be as instantly recognisable as the later black/gold ‘Plexi’ livery and script logo. However, credibility with Marshall cognoscenti will definitely be assured.
Feel & Sounds
The Studio JTM warms up smoothly and quietly with practically zero hiss or hum. The two preamplifier channels are permanently on, so you simply plug into whichever one sounds best, although the third option of joining both channels with a short patch lead between the unused input jack sockets provides the most versatile solution.
Most ears will hear the High Treble input as slightly too sharp and the Normal input as a little too warm, but with both channels on you can quickly find an ideal balance by blending the two volume controls and then fine-tuning with the JTM’s passive EQ.
(Image credit: Future / Phil Barker)
As most people know, the original Marshall JTM45 was inspired by Fender’s Tweed-era 4x10 Bassman, which was also powered by a pair of 5881 valves. The 5881 was developed by Tung-Sol Electric as a high-quality ruggedised version of the 6L6GB and proved ideal for guitar amp use.
Early JTM45 models used the same valve, but 5881s weren’t readily available in 1960s Europe, so Marshall experimented with alternatives, changing to M-OV’s KT66 for a short time before finally settling on the EL34.
The Studio JTM has a different feel to the ‘Plexi’ version with a warmer and less aggressive vibe that’s partly down to the 5881’s frequency response and power curves. Those classic blues/rock tones of the late ’60s are reproduced with unerring accuracy, especially when the amp is partnered with a Les Paul. Add treble boost or a fuzz pedal between the guitar and amp, and the results are even more convincing.
(Image credit: Future / Phil Barker)
Used on the 20-watt setting, there’s plenty of power and headroom to handle the average unmic’d pub gig, although no master volume control means you have to wind up the loudness to experience the JTM’s rich overdrive character, or add a suitable distortion pedal.
Switching down to the five-watt setting makes it easier to drive the JTM into clipping while retaining plenty of dynamic punch. Alternatively, cleaner settings emphasise the 5881’s smooth frequency response and clarity, making the Studio JTM a great pedal platform, with the advantage of a series loop to bring the best out of reverb, delay and modulation effects.
The speaker-emulated DI works well, offering a consistency that’s difficult to achieve with microphones and sending a clean low noise signal into your console. However, with no dummy load you need to keep the JTM connected to a speaker cabinet, so there’s no easy silent recording option for late-night home users.
Verdict
Marshall’s Studio JTM is an essential addition to the Studio series, nailing the classic British blues/rock sound while satisfying the trending demand for lighter and more portable amplification.
Visually, the Studio JTM looks the part, too, especially when teamed with a matching 1x12 or 2x12 extension cab, and at just under 10kg it’s an easy single-handed lift, unlike its 1960s ancestors.
Specs
(Image credit: Marshall Amps)
PRICE: $1,749 / £1,075
ORIGIN: UK
TYPE: All valve pre and power amp
VALVES: 3x 12AX7 preamp, 2x 5881 power amp
OUTPUT: 20W RMS into 16 or 8 ohms, switchable to 5W
DIMENSIONS: 500 (w) x 230 (d) x 240mm (h)
WEIGHT (kg/lb): 9.5/21
CABINET: Plywood
CHANNELS: 2, non-switching
CONTROLS: Normal Loudness, High Treble Loudness, Bass, Mid, Treble, Presence
FOOTSWITCH: None
ADDITIONAL FEATURES: Speaker‑emulated line out, fixed level series effects loop with defeat switch, High/Low power switching (20/5 watts)
OPTIONS: None
RANGE OPTIONS: The Studio JTM is also available as a 1x12 combo ($1,949 / £1,279), with a matching 1x12 cab ($1,099 / £565) and a vertical slanted 2x12 cab ($1,399 / £765), both loaded with the Celestion G12M-65 Creamback
Nick Guppy was Guitarist magazine's amp guru for over 20 years. He built his first valve amplifier at the age of 12 and bought, sold and restored many more, with a particular interest in Vox, Selmer, Orange and tweed-era Fenders, alongside Riveras and Mark Series Boogies. When wielding a guitar instead of soldering iron, he enjoyed a diverse musical career playing all over the UK, including occasional stints with theatre groups, orchestras and big bands as well as power trios and tributes. He passed away suddenly in April 2024, leaving a legacy of amplifier wisdom behind him.
