British Style 18W TMB Amplifier Kit
Amp Kit Difficulty Level
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Please read our article 'Mojotone Amp Kit Building Primer' along with our amp kit disclaimer located in the Specs tab 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: ECC83/12AX7 (3)
- Output Tube(s): EL84 (2)
- Rectifier Tube: EZ81
- Transformers: Power - 18W (7000018), Output - 18W (7000118)
- 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.
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 email@example.com 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 firstname.lastname@example.org. 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
Ratings & Reviews
Great sounding amp with a few flaws in the documentation
by Tom Arbogast -
Nice amp with a few documentation flaws.
1. The Wiring Diagram shows the Mains and Standby switches oriented in the wrong position, they should face up.
2. The earth ground at the AC jack should have a dedicated chassis ground not shared by any other component. It's unsafe the way it's shown in the wiring diagram.
3. The inputs, pots, and pre-amp section should all have a common star ground.
4. The ground for the can capacitor mounted to the top of the chassis should be connected to the star ground for the power section.
5. The lead on the indicator light to the AC jack is too short!!! Come on guys!!!
6. The 130 Ohm resistor and 25uF capacitor are shown too close together in the wiring diagram. The capacitor should be at least 1/2" away. Both components and several other resistors in the power section should also be raised off the turret board to allow adequate air flow. There is no mention of this in the instructions.
When assembled correctly, the amp sounds great!
by Heath McDonald -
The jcm preamp makes it so you can really gain this thing up if you want to and with the master volume, at lower levels. Mid heavy, really cuts through. You can go from really great cleans to AC/DC (tnt) tones to early pearl jam and then you can push it hard with a pedal some early Metallica tones. It’s waaaay louder than I thought it would be capable of. Really versatile and lovely amp, great idea with the jcm preamp. A much more versatile addition for me than the 18 watt would have been. Great all around ‘er.