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Marshall ST20C Studio JTM 1 x 12-inch 20-/5-watt Tube Combo Amplifier

20/5W, 2-ch 1x12" Tube Guitar Combo Amplifier with Celestion G12M-65 Creamback, 3-band EQ, Presence, DI Out, and FX Loop
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A Return to Marshall’s JTM Roots

Marshall’s Studio series has long served as a Sweetwater favorite, as it perfectly packs many of the company’s iconic amplifier models down into compact, gig-and-studio-ready combos and heads. From the Super Lead to the Silver Jubilee, the Studio series encompasses almost the entirety of Marshall’s long history — with the ST20C Studio JTM, it reaches all the way back to the beginning. This 20-watt, 1 x 12-inch combo amplifier precisely replicates the creamy highs, loose lows, and smoky overdriven tone of the original Marshall 2245 — the platform that arguably defined the biting sound of British blues rock, while also setting the stage for Marshall’s later amplifier creations. Plus, while it’s certainly a vintage throwback, the ST20C Studio JTM comes equipped with all the Studio series’ usual bells and whistles, including a 5-watt power scaling mode, FX loop, and speaker-emulated DI output. Vintage-inspired from the metal “coffin”-style logo to the levant front covering, the UK-built ST20C Studio JTM is a top-tier tonal tribute to the model that began the Marshall legend.

A tonal tribute to Marshall’s famed 2245/JTM 45

More than just an aesthetic tribute to Marshall’s early days, the ST20C Studio JTM’s dual 5881 power tubes and trio of ECC83 preamp and phase inverter tubes match the original 2245. In comparison to the later EL34-equipped Marshall models that would define hard rock in the 1970s, the ST20C Studio JTM’s tone harkens back to the birth of British blues-rock, perfectly capturing the loose bass, rounder response, and compelling natural compression of its JTM inspiration. Overall, the ST20C Studio JTM supplies an extraordinarily versatile tube tone that can take you from stadium-ready power-chord rhythms to dark, moody blues lines without breaking a sweat. And if you’re after just a touch more control, Sweetwater guitarists recommend trying out the time-tested trick of patching both channels together and blending their tones!

Vintage-inspired Celestion G12M-65 Creamback speaker

Originally released amid rock’s mid-1960s revolution, the Celestion G12M Creamback found in many a vintage Marshall amplifier helped define the sound of the burgeoning blues-rock scene. It’s arguably Celestion’s most iconic ceramic magnet speaker, gracing the records of countless all-time greats, including Jimi Hendrix, Eric Clapton, Jimmy Page, and Jeff Beck. The Marshall ST20C Studio JTM combo’s G12M-65 retains the same vocal-like midrange, creamy highs, and aggressive overdriven tone of the original, only with a significantly higher power rating and a slightly improved low-end response to better suit the modern guitarist. For players who clamor for the raw and organic dirty tones that set the stage for Marshall’s dominance of the classic rock era, Sweetwater guitarists agree: the Celestion G12M-65 speaker is tough to top.

Loaded with all the player-friendly features you need

Consider yourself lucky, because the Marshall ST20C Studio JTM sports plenty of onboard features not found on the original 2245. An onboard FX loop makes integrating your pedals and external processors a breeze. Attaining cranked tones at listenable volumes is a breeze thanks to a power reduction circuit. You also get a speaker-emulated DI output for easy recording or routing to a PA. You’ll value the ST20C Studio JTM modern flexibility almost as much as you appreciate its classic tone.

Early-era Marshall aesthetics

Far from the later plexi-equipped, script logo Marshalls that we all know and love, the Studio JTM series reaches back to an earlier time in the Marshall legend — when Marshall amps still wore their American influence on their sleeve. This amp’s levant front covering, gold piping/beading, and handsome metal Marshall “coffin” logo look as though they rolled right out of Jim Marshall’s workshop, beaming with early 1960s style. And perhaps best of all, the ST20C Studio JTM boasts a high-end enclosure crafted from finger-jointed plywood for a lighter weight and superior sound.

Marshall ST20C Studio JTM 1 x 12-inch 20-watt Tube Combo Amp Features:

  • 2-channel, 20-watt tube combo amplifier inspired by Marshall’s early 2245 model
  • Dual 5881 power tubes, 2 ECC83 preamp tubes, and an ECC83 phase splitter capture the creamy highs, loose lows, and exceptionally dynamic overdrive of the original JTM
  • Celestion G12M-65 Creamback speaker offers a slightly higher power rating and enhanced bass response over the original Creamback found in early Marshall amps
  • High Treble and Normal channels can be patched together for endless tonal experimentation
  • Treble, Middle, Bass, and Presence knobs to dial in your sound to perfection
  • Speaker-emulated DI output for easy recording and straight-to-PA gigging
  • FX loop makes it a breeze to integrate your favorite time-based and modulation pedals
  • JTM-inspired aesthetics, including levant front covering, metal “coffin” logo, gold piping, and fawn fret
  • Premium finger-jointed plywood enclosure
  • Handbuilt in the UK Marshall factory

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Tech Specs

  • Type: Tube
  • Number of Channels: 2
  • Total Power: 20W (5W)
  • Speaker Size: 1 x 12" Celestion G12M-65 Creamback
  • Preamp Tubes: 2 x 12AX7 (preamp), 1 x 12AX7 (phase)
  • Power Tubes: 2 x 5881
  • EQ: 3-band EQ, Presence Control
  • Inputs: 2 x 1/4" (High Treble), 2 x 1/4" (Normal)
  • Outputs: 5 x 1/4" (4/8/16 ohms), 1 x 1/4" (DI out)
  • Effects Loop: Yes (on/off switch)
  • Power Source: Standard IEC AC cable
  • Height: 18.1"
  • Width: 19.7"
  • Depth: 10.4"
  • Weight: 39.2 lbs.
  • Manufacturer Part Number: ST20C

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Customer Reviews

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Rated 5/5

This is THE amp!

This is one of those amps that you can plug your guitar into with all the amp's knobs can be at noon and it will sound glorious. There's no unusable setting, it's never too harsh and remains full regardless of where the eq is set, the amp just doesn't sound bad.

If someone uses this amp and says they are getting a bad sound out of it, I'd wager they most likely don't know what they're doing.

The Celestion Creamback 65 speaker is the best speaker for a Vintage Marshall type amp. It takes the Harsh frequencies and tames then into something musical. I would not like this speaker in a Fender-type amp, but it suits a vintage Marshall amp perfectly.

The cab is wide and thick, there's a depth to that which gives the amp a bigger sound, maybe this influences the amp's feel. It sounds and feels much bigger than it looks, has the feel of a cranked Marshall through a half-stack, I feel.

This amp is for someone who wants the REAL deal. There are tons of clones of this amp, but cannot take the place of it. This is well made, craftsmanship is top-notch, it is every bit of good I hoped for!
Music background: Praise and Worship
Rated 5/5

JTM Perfection In A Box

I saw Nashville ace, Tom Bukovac, getting some very fine vintage rock tones out of one of these and decided to give it a shot. I own all of the recent releases of the Studio series for my rehearsal / recording space. This is probably my favorite for most rock and soul applications. It cleans up really well but still has that nice top end sparkle. If you want a little crunch at low volumes, hit those strings just a bit harder and the preamp responds perfectly. If you want tube saturation without going deaf, the low wattage setting works great - with no compromise like some amps that lose all their detail when you shut off a valve or two.

It's an inspiring little amp to play. It's also a lot of fun to get near exact sound as Jimmy Page, Hendrix, Joe Perry, Gary Richrath, etc., My overdrives and fuzz pedals cook on this thing. A little is all you need. I use a Chase Bliss Automaton for my drives and put an Eventide H90 in the effects loop. Zero disappointment. Very satisfied. It's right up there with the Magnatones, Bensons and Two Rocks.
Music background: Lifer
Rated 5/5

Great sound

I bought this amp because I love that early sound. Man this is a sweet amp.
Rated 5/5

Love this compact combo amp for its classic sounds

I recently acquired a JTM Studio Combo (ST20C) 3 months after getting the SV-20C. The cosmetics alone are worth the price of admission, but the real secret in this fire-breathing monster is the voicing. The JTM gets the Clapton "Woman Sound" in a tiny manageable package. The 12" Celestion Creamback is perfectly matched to the 6550 output tubes. Use this if you want to sound like vintage classic rock. Get the SV-20 if you want to emulate the harder, more aggressive rock of AC/DC, Free and Bad Company.
Music background: 30+ semi-pro guitar
Rated 4/5

Update on repair

This is an update to my previous review (above?)on this amp. I took it to a local designated Marshall Factory Service outlet and they reported the following:

"Resistor R4 was unsoldered on one end. Most of the standing up components had inadequate solder. I could see light through the solder holes of the fuse clips. Several standing 1W resistors easily pulled off with a light tug. Went through the amp and resoldered most of the big components. The tube sockets were great and the small components and caps seem fine. Tubes tested good as new. Reassembled and tested."

So as suspected, the QA performed on this particular amplifier was inadequate. Amp is back in my "studio" and being played. Marshall needs to sharpen their game a bit.
Music background: Intermediate

There are countless "British"-style guitar amplifiers out there, but take it from the lifelong guitarists and tone connoisseurs at Sweetwater, when it comes to Marshall tone, there's nothing like the real thing. We've played them all, from vintage JTM45s and the ultra-cool Plexi reissue to modern handmade masterpieces such as the JVM410. There isn't a model among them we can't recommend with total confidence, and that includes their more affordable models too, like MG, DSL, and Code series amps. Thanks to our tight relationship with Marshall, Sweetwater's always on the cutting edge of their latest designs, custom models, and limited-edition gems. If you want iconic tone from across the pond, you want Marshall, and your Sweetwater Sales Engineer will help you find the perfect one.

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