British Style 18 Watt TMB 1x12 Combo Amplifier Kit

4 Reviews
$511.09 to $925.00
Weight: 57.65 lb

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On Back Order

Kit Build Difficulty: 

This kit will ship within 3-5 weeks from order date.

Please read our article 'Mojotone Amp Kit Building Primer' along with our amp kit disclaimer below before buying this kit.

Mojotone's 18-Watt TMB Amplifier Kit addresses a common mod made to a classic circuit, but with a few new flavors of our own. The TMB is based on the circuit used in vintage Marshall models 1958, 1973, and 1974 (more affectionately known as the '18-watters'). Marshalls were only produced between the years 1965 and 1967, but were highly sought-after for having massive sounding JTM-45-like tones in a smaller, more manageable package. Because they were produced in comparatively low quantities, these amps still remain a 'lost ark' today.


18-watters became popular studio amps for many players and were used, at times, by everyone from Gary Moore, to The Pretenders, to AC/DC. Over the years, some players have reported having no use for the amp's original tremolo channel and have opted to replace the tremolo controls with a 3-band EQ, since the original amps were only equipped with a single tone control for each channel. In the Mojotone version, we have done just this, only we have integrated the preamp from our British 800 kit (based on the original Marshall JCM 800 circuit) for a lean and mean, hot-rodded gain sound. We have also integrated a master volume control so this monstrous sound can be harnessed and used in any size room.


Two EL84s give the amp's normal channel a warm and round character which, when volume is pushed higher, begins to break up into a smooth grind perfect for blues rock and classic rock rhythm sounds. On the dirty channel, one can access screaming lead tones perfect for everything from dim dirty grunge all the way to saturated hair metal sustain!


  • Class Type:A All Tube Amplifier
  • Output:~18 Watts
  • Circuit:1974 / 2204
  • Bias Type:Cathode Bias
  • Build Time:~6 hours
  • Preamp Tubes:JJ ECC83/12AX7 (3)
  • Output Tube(s):JJ EL84 (2)
  • Rectifier Tube:JJ EZ81
  • Transformers:Power - 18W (7000018), Output - 18W (7000118)
  • Speakers:Mojotone BV-30H 12" 8 ohm Speaker
  • Cabinet:British 18W 1x12 Combo Cabinet
  • Hardware:British 18W Small Parts Kit, British 18W Chassis, Front & Rear Faceplates, 10' Removable Power Cord

Disclaimer: Some of the parts contained in this kit are subject to availability.

Mojotone reserves the right to change or substitute any and all of the parts contained in this amplifier kit without advertisement or notification to the buyer. Part substitutions made by Mojotone are guaranteed not to affect the integrity or operation of your amplifier kit. Time estimates listed are from start to finish. If you are new to tube amplifiers, additional time may need to be factored.

When purchasing a kit from Mojotone, you will receive the following documentation.

1. Schematic

2. Wiring Diagram / Layout

Our beginner level kits such as the tweed champ and tweed deluxe include a manual. If you purchase a kit from Mojotone and do not receive these documents, you can obtain copies by emailing or calling 800-927-6656. The Mojotone staff is available Monday through Friday from 8:30 a.m. to 5:00 p.m. EST unless otherwise closed.

Mojotone kits include the best quality parts that are available at the time of purchase. If a substitution is required, our team will use parts that are of equal quality to ensure the integrity of the kit build remains the same.

Building a fully functional amplifier kit is not an easy task. Before building a kit, one should have the ability to properly solder as well as read and understand a schematic and wiring diagram. While we do our very best to ensure all documentation is current, the included documentation is meant to serve as an overall guide to building the amplifier. Simply following the schematic and wiring diagram does not guarantee you will have a fully functional amplifier. In fact, post build troubleshooting is a common issue across all builds.

Our staff is available to assist with basic troubleshooting needs. There are plenty of online videos available that are helpful with most post build issues. Technical staff is available via email by sending a message to You may also call our sales team to discuss build problems, dial 800-927-6656 and press 1 for sales.

Building a tube amplifier takes time, dedication, resources and most importantly... Skills! The experience of building an amp can come with some frustration, the reward of completing the build is definitely well worth your time. Please review the wiring diagram, schematic and manual (if applicable) prior to making your purchase. Mojotone will not accept any returns on amplifier kits and/or parts that have been assembled, soldered or modified.

This amp kit also comes with the following documents. Please feel free to view and/or download them:
British 18 Watt TMB Schematic
British 18 Watt TMB Wiring Diagram
British 18 Watt TMB Manual

Ratings & Reviews

4 reviews

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2/17/2021 1:42 pm

Get one!

by anonymous

This is my third Mojotone kit, and it amazes me every time that the MJT crew includes every part, not a single part missing out of a thousand+ components in my experience. Well done!

I was thinking about building the 1974x kit, but I didn't have a use for the tremolo channel, like the TMB ad says. The lure of having an 18 watt JTM channel with a JCM800 TMB channel, instead of the tremolo, made the 18 watt TMB an easy choice for me.

I'm fairly new to building still, so when I saw the new instructions and realistic wiring diagram layout, the sale MJT had on this model was all it took. I bought the combo version, with 1x12".

There are some errors on the wiring diagram layout, pin 4 and 5 of socket V1, should have a jumper between those pins.

Also, the input jacks of the JTM channel, the top jack, the green wire should be connected to the top most lug, not to the lower 68K resistor connection.

I got a 3-lug ground strip instead of the pictured 4-lug terminal strip for the PT ground point, had to do my own thing, but it turned out great.

Aside from that, I couldn't have built this kit without the new-friendly instructions and wiring diagram. I also couldn't have found the errors without the forum at TheGearPage.c.m, those guys are an incredible resource if you get stuck, or have questions.

The important part: how does it sound? Huge, in small way. Barely enormous. It sounds like a JTM and a JCM800 to my ears, and at a comfortable volume, but without the wall pounding thump of a 45W/50W and 4X10's/12's. It's very studio and bedroom friendly. Even at low volumes it gets raw on the JCM channel, gritty and spitty. The JTM channel has a nice clean tone, pedals are insane! Throw an OD at it, and it can scorch in either channel.

I really thought it was going to be much louder than a 15 watt 10" Princeton I built, but it's not. The raw and gritty tone can be had from the JCM channel at very low volume, thanks to the Master Volume. It can get loud of course, if you crank it.

The tones, and the response that can be coaxed out of this amp, are exactly what I was hoping for, and I had a lot of fun building it. Get one!

2/17/2021 1:42 pm

Highly recommend this kit to anyone.

by anonymous

This was my third build, and I really enjoyed it. The turret style board made for a very pleasant build and I really took my time with lead dress. I did use different wire than what came with the kit because I prefer cloth covered wire (mainly for aesthetics). I ended up using modern cloth covered wire with vinyl coating underneath, but I am sure the vinyl coated wire that came with the kit would've been perfectly fine. Absolutely LOVE this amp and it became my all time favorite very quickly. Gives great Marshall Plexi tones when the gain is cranked, and the Master Volume allows me to get that tone in the house without an attenuator. I love the clean tones from this amp as well, and the range of tone shaping you can do with the TMB controls is great. The amp takes pedals extremely well also, but I've actually just enjoyed playing it with just a bit of reverb my Benson Dizzy Bird (Tall Bird + Vinny combo). I mostly play this amp at lower volumes, but it gets plenty LOUD when you want it to. Highly recommend this kit to anyone.