Our Marshall JCM900 Combo Review: How Good Is This Amp?

Have you ever wondered why players like Hendrix and Billy Joe from Green Day chose and stuck by the JCM900 over any other amp that money could buy?

The Marshall JCM900 is a very controversial combo in the guitar universe. It gets as much bad rep in the industry as it does praise, which makes you wonder, is it any good?

It’s a popular tube combo model that offers the classic vintage sound that tube amps are known for. Most people call it the last of the proper Marshall amps. When Marshall came up with the JCM900, they used transistors and diodes to create more distortion. Read on to learn more about this amp.


Amp Type: Tube Amp

Speaker Configuration: 2x12

Speaker Details: Origin Celestion G12T-75 12" Speakers

Range of watts: 40- 100 Watts

Power tubes: EL34 / 6CA7 / KT77

Preamp tubes: 12AX7 (x3), EL34 (x2)

Channels: 2

Foot switchable

There are two types of JCM900 series: the master volume range and the more popular dual reverb range.

HI Gain Master Volume SL-X

The Master Volume range was designed for uncompromising high gain rather than clean sounds. They use an extra ECC83 preamp valve in the gain stage for that extreme gain, creating a gain-drenched front end. They have unique twin master volume controls for the benefit of switching volumes when playing rhythm and solo.

They come with two gain controls that provide a versatile sound range, from a vintage Marshall crunch on the lows to the typical metal rage sound on the maximum. This must be why Hendrix enjoyed playing with this particular range.

Volume and Wattage

This combo’s forte is in the louder range of its volume. You can hear and feel the valves open up and the sound tighten up. The combo pairs really well with Celestion Greenback G12M Speakers. The open-back cab gives a much lighter sound.

Wattage in an amp usually correlates to how much output the amp can give you. Don’t mistake this to mean the higher the watts, the louder or better the amp. The JCM900 uses really good quality 5881 tubes—two in 50 Watt models and four in 100 Watt models for their unique distortion.

JCM900 combos also surprisingly come with the option to change the wattage. The 50-watt models can go as low as 25 watts. On the other hand, the 100-watt models can go as low as 50 watts at the flick of the high and low switch at the back. With the 50-watt version, you can squeeze more out of the combo without frying the tubes.

Build Quality

This 90s combo has a solid build that was typical of the good old UK amp builds. The original combos and amps were built with birch ply, but later on, Marshall switched to medium-density fiberboard.

The back of the amps are usually built out of galvanized steel, the heavy grade kind to protect the interior. It has excellent Drake transformers and a heavier gauge chassis than most Marshall amps. It is, however, notorious for getting scratchy pots after a while, though.

Tone Quality

When it comes to tone quality, you already know what to expect from a classic 90s tube amp. The JCM900 does lack a bit on the low end, but it makes up for it with its midrange. The combo has more midrange than most Marshall amps.

This makes the combo especially good for rock and metal sounds. However, the JCM900 doesn’t have the cleanest tone out there, if that’s what you’re looking for. A lot of people have described the JCM900’s tone as fuzzy. The main reason why it gets so much flak, though, might be due to channel B, which gives a much thinner sound than channel A.

As much as this combo is hailed for its crunchy rock tone, you can still get some nice clean sounds from it.

Controls and Effects

The JCM900 combo also gives you a lot of control over the kind of sound you want. Each channel has its own reverb control and master volume control.

Channel A has a preamp gain control, while channel B has a lead gain control whose lower settings have a little overdrive and higher settings for maximum drive and sustain.

Technically, they also have a distortion effect thanks to the diode clippings, which act like a built-in distortion pedal. The combo also comes with a four-band EQ that will let you customize the tone as much as you desire. These include treble, middle, bass, and presence controls.

Other than the reverb, the JCM900 also comes with an effects loop with level control at the back. This allows you to link and go with either floor pedals or rack effects. The higher levels go with modern effects processors, while the lower levels go with floor pedals.

Tips for Handling Your Marshall JCM900 Combo

  • Consider setting your combo on standby for a minute or two before playing. This will help warm up your tubes.
  • Make sure to switch to mono and not stereo if you want to be using four of the preamp tubes instead of two.
  • Use a stereo cord for the footswitch.
  • Do your research when replacing the tubes. Find out more here about the best tubes for the JCM900.

Final Thoughts

As much as the Marshall JCM900 might get a lot of criticism from many players for being rigidly crunchy, it’s still the best at what it does. At the end of the day, people will have different opinions on the JCM900. We believe that the JCM900 combo is slept on and give it a solid 7/10.

If you’re still not convinced, check out other alternatives by reading our article on finding the best Marshall combo amp.


  • Marshall JCM900

    My "day job" used to be teaching but I decided to give that up to play music full time. I have gigged all over the world playing in bands or as a solo act since then. I still have a passion for teaching others anything related to music. Writing content for gives me an opportunity to combine my love of music and education.

Leave a Reply

Your email address will not be published. Required fields are marked *

Quick Links To Our Best Content
Affiliate Disclosure
We unbiasedly and independently review products on our website. We are funded by affiliate links. We may earn if you make a purchase through our links. As an Amazon affiliate we may earn from qualifying purchases
Contact details
(use contact form first please)
Email: info () 
Address: 308 Circus Drive
Icksberg  PA 17037, USA
Hours: Mon - Fri 9am - 5pm
Phone: +1(717) 220-9204