Trinity 18 Kit


We have four two channel versions of the Marshall 18 watt amps that you might want to consider – the sIII, Custom Plexi, Plexi MkII and TMB. All 18 watt amps incorporate Treble, Midrange, Bass, Gain [volume] and Volume [master volume]. The second channel (Normal Channel) has Tone and Volume controls.


The sIII is a medium gain amp and is voiced to do the early plexi/JTM45 sound very nicely. The range of tone is from spanky clean to Marshall grind. You can get a great Clapton Bluesbreaker sound and Hendrix as well. This amp can handle Blues-Rock, Country & Reggae. The Second channel (Normal Channel) is same configuration as the Tremolo channel from the original 18 watt design but without Tremolo.

I just wanted to say one thing...WOW. This thing is a monster. Your instructions are extremely well thought out as far as what steps to logically take and when, as well as a lot of extremely helpful information that I feel would help even the most novice of builders. This thing has got some breath in it. It's incredibly touch responsive and the range of tones that I can get out of such a seemingly simple design is nothing short of mind blowing. My hat definitely goes off to you and everyone that put work into making this amp design come to life. Thank you from a very VERY satisfied customer.

David G., Raleigh, NC (Trinity 18 TMB Kit) (Trinity 18 Kit)

Plexi MkII

Is based on the Plexi Super Lead preamp design with selected ‘brown’ components.  Hot licks but with a very surprising clean tone with gain turned down. This baby can really move some air! Crank up the normal channel and it really gives up the goods! Lots of crunchy to high gain AC/DC tones for days. The TMB side cranked up is great going from clean to mean. Leave the gain low and crank the master and there is quite a lot of headroom with big fat cleans. The fat switch fattens up the TMB side and makes it a bit fuller spectrum of sound. Clip here.


The TMB amp is a high gain amp that does the 80s sound very nicely. It is intended for musicians who want plenty of grind. It does ZZTop very nicely. It is both responsive and aggressive. The second channel is the Normal channel from the original 18 watt design. This amp does classic rock crunch to metal.

The inputs can be jumped on all of our 8 watt amps. If you want to hear some clips of these fabulous amps, go to 18 WATT CLIPS or check out the Clippage section of our forum.

Custom Plexi

The Trinity Amps Custom Plexi is a 6V6 powered amp authentic to the Marshall 1959 Super Lead Plexi and it does sound excellent. It has the Classic Marshall tone and crunch in a usable 18 watt package.
Preamps, tone stack and Phase Inverter are identically voiced to the Plexi Super Lead.
1 Watt Carbon Film resistors are used.
Running at 390V, with an octal socket based solid state rectifier powers two cathode biased JJ 6V6Ss. The rectifier can be swapped out for a 5AR4 for lower voltage to ‘brown’ out the sound and give it a more compressed feel. The fat switch fattens it up the TMB channel and increases the sound spectrum.
The Classic Marshall tone you’ve heard a million times!


Thor is the god of thunder, lightning, storms and strength. A classic name for this powerful sounding Trinity Amps product.

The Trinity Amps Thör is a 20 watt, fixed-bias 6V6 powered amp authentic to the Marshall JCM800 2203  Lead Series Master Volume amp based on original work by RobRobinette.com and it totally delivers. In addition to the Lo Sensitivity input, Thör employs a cascaded Hi  Sensitivity  channel. With a pre-phase inverter master volume and a cold biased “cold clipper” gain stage and the circuit tweaked to deliver an aggressive but sweet overdrive tone, Thör has the quintessential Marshall tone and crunch but in a very usable 20 watt package. The Preamp, tone stack and Phase Inverter are identically voiced to the JCM 800 2203. There is some frequency compensation employed to retain the 2203 circuit and smooth it out.

Running an octal socket based solid state rectifier with choke, the 400V  supply two JJ 6V6Ss. There is an added  Clipper switch to select either JCM cold clipper or the SLO cold clipper. The gold, brushed aluminum look front  panel is intentionally reminiscent of the original JCM 800s.

Get the Classic Marshall tone you’ve heard over a zillion times!


What differentiates our kits from others is part quality, fit, documentation and support. Included are all components: Mallory 150M caps; CARBON COMPOSITION or FILM resistors; CLIFF jacks, ALPHA pots, JJ 32/32uf filter cap; Belton Micalex tube sockets; tube retainers & shields; 1/8″ thick GP03 Turret Board with large size KEYSTONE Turrets; CARLING switches; 6A impedance switch; All 22 gauge hook-up Wire; Pre-twisted heater wire; BELDEN Co-Ax cable; All Mounting hardware, spacers and nuts; Hand-Made Plexi Gold Front faceplate with 4 Inputs; MARSHALL control knobs; Pre-Cut 0.09″ Aircraft Aluminum Chassis with tapped holes for mounting screws and silk screened rear chassis; 100 Page Assembly guide; large 11″ X 17″ size layout and schematic drawings and REAL Support.

The transformers are custom made by Heyboer to the exact specifications of the original Radio Spares set used in the early Marshall 18 watt amps. The output transformer has convenient flying leads, multiple secondary windings and the unused ultralinear taps on the primary side has been wound to 5K. This is an excellent 18 watt transformer.
Supported AC Primary voltages 110, 120, 220, 230, 240 50/60 Hz

The vintage looking, small box Plexi-style sized chassis is based on standard dimensions that fit most commercially available cabinets including Trinity Amps. Find more details at Trinity 18 Watt Forum Link.










18 Watt Plexi v6 Kit – Michael Blakemore

I have finally had enough down time off the road, to start and finish building my 18watt Plexi with dual power tubes.
It is up and running and sounds fantastic!! You really took your time crafting this thing and I just wanted to say thank you for taking the time to do so and sharing it with everyone. I have built and played 18 watters before and they are always lacking in something, but yours keeps up with my 50 and 100 watters in feel, clarity, etc. So thank you!! I am very, very pleased.
I have built various kits from Weber and Ceriatone over the years and the Trinity kit by far is the most thought out and professional kit I’ve ever had the privilege to build. Everything down to the tube socket screws being able to screw into the chassis without the use of nuts and everything is just brilliant!! Again, I am not only pleased with the sound, but the craftsmanship of the parts provided.
Again, I just want to say thank you and I will be doing my best to pass the word along for you guys. There is no doubt in my mind as well, that my friends and colleagues will be very curious about this amplifier and a few will even hound me to build them one. Here is to hoping!! 🙂

Spamming My Love for this 18 Watt Amp! – David Golladay

Just wanted to share my experience with building the 18 Watt TMB version.This is my first guitar amp build ever, but I have experience with pedals and various amateur radio transceivers. The instructions were top notch, and I personally feel that with just a bit of reading and maybe practicing soldering with a couple “dummy” components that even a beginner could have success with this amp. The board is very clean looking without a large ground buss hanging in the breeze, all components are top notch and very well thought out.
I opened her up and the first night, despite chomping at the bit to get going, I just sat down with the box and the BOM and just made sure everything that was needed was included. Everything that should have been in there was, as well as a couple extra components for adding the V6 option later and a couple “tweaking” components. I was able to hook up and test the power supply section and everything worked well so far.
I completed everything, and double checked my wiring and did the initial power up test while hooked up to a light bulb tester. All was well until I hooked up the guitar and absolutely zero signal! Frustrated, I went and checked all the voltages and they looked decently fine so I looked over my schematic and layout which I’d highlighted as I went. Not surprisingly…there was a small ground connection to the main power ground that I’d not highlighted.
After making this connection, and firing it up again…this thing really sings! The tones that you can squeeze out of it are amazing and the way it responds to just slight changes in picking is just phenomenal and borderline indescribable. This amp is a complete joy to play, was a blast to put together and overall, I’m just proud of it…
Two bits of advice to anyone wanting to get this kit or who just don’t know…18 Watts is still QUITE LOUD…plan accordingly. Secondly…the builders guide mentions checking all connections no fewer that 5 times, make sure you do that…and then check them once more. Even a seasoned builder of electronics can overlook something when giddy with excitement to get going.
Thank you Trinity for an amazing instrument!!!











  • Channels: 2
  • Controls Ch.1: Volume; Tone
  • Controls Ch.2: Bass; Middle; Treble; Gain; Volume
  • Power output: 18 Watts
  • Preamp Tubes Required: 3-12AX7
  • Power Tubes Required: 2 – EL84
  • Rectifier Required: EZ81
  • Bias: Cathode
  • Choke: no
  • Outputs: 2
  • Speaker Output: 4, 8, 16 switched
  • Chassis Weight: 12 lbs.
  • Switches: Ch. 2 Boost; EL84 / 6V6 switch on v6 Model
  • Chassis Dimensions: Head: 2.5” H x 20” W x 6.5” D


  • Channels: 1
  • Controls Ch.1:  Bass; Middle; Treble, Presence; Volume; Master Volume
  • Power output: 20 Watts
  • Preamp Tubes Required: 3-12AX7
  • Power Tubes Required: 2 – 6V6
  • Rectifier Required: Solid State Module
  • Bias: Fixed
  • Choke: yes
  • Outputs: 2
  • Speaker Output: 4, 8, 16 switched
  • Chassis Weight: 12.5 lbs.
  • Switches: Clipper –  JCM / SLO
  • Chassis Dimensions: Head: 2.5” H x 20” W x 6.5” D

Video Samples

Thör HI Sensitivity Demo

Trinity Amps 20 Watt Marshall 2203 Circuit Hi Sensitivity Channel Demo

Thör Lo Sensitivity Demo

Trinity Amps 20 Watt Marshall 2203 Circuit Lo Sensitivity Channel Demo

Trinity 18 Classic Rock Demo
Trinity 18 sIII Demo
Trinity 18 sIII Demo
Trinity 18 Plexi

Pricing Options

Canadian Customers Click 'Inquire' to receive up-to-date CAD pricing and shipping. Include postal code for quote.
We price affordably while managing fluctuating exchange rates with our suppliers. Our CAD best price guarantee accurately reflects our costs.
18 Watt Head Kit Package
$590 USD
18 Watt kit includes all components except tubes, speaker and cabinet.
Thör Head Kit Package
$625 USD
Thör kit includes all components except tubes, speaker and cabinet.
Head Cabinet
$260 USD
Custom Head Cabinet
VRM (Voltage Regulation Module)
$42 USD
Electronic Attenuator

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Payments can be made through PayPal to sales@trinityamps.com. Payments can also be made using Interac e-Transfer, money order, cashier’s or personal check to Trinity Amps Inc.

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All prices are listed in US dollars. Orders ship from Brighton, Ontario, Canada, applicable taxes not included. Specifications and prices subject to change without notice.

Trinity Amps Inc.
+1-613-438-5854 Canada EST

14656 County Rd. 21
Brighton, ON
K0K 1H0