Trinity 18


These amps sound and feel like bona fide Marshalls, albeit quieter, with a design “borrowed” from the early Watkins Dominator circuit. The truly exhibit the much sought after, famous Marshall crunch. Marshall 18 Watt amps were built between 1966 and 1968, or so, and only a few hundred were made.
The two-channel amplifier does away with negative feedback, allowing the amplifier to run “open loop” or wide band. This is why the 18 Watt sounds full and rich at low or high volume levels. These ‘features of design’ are very much a part of the distinctive tone.

I have to tell you: it sounds so amazingly incredibly fricken good. It's so much better than what I ever imagined it to be, it's response is fast and tight covering all frequencies - top frequencies are cutting their way through the air, with a lot of edge and it does NOT sound thin and disgusting. Mid-frequencies are in- your-face punchy, and the bottom end is so tight and clear. There are so many natural harmonics in this amp, I don't even know where to start.

Eivind, Sogne, Norway (Trinity 18 Plexi)

We have added to the tonal variety of the original by hand-building five 18 watt Marshall type amps to cover almost all of the Marshall era vintage tones. The sIII, TMB, Plexi, Plexi MkII and the v6. We can mix and match channel voicing, for example Plexi TMB channel with sIII Normal channel.


The Trinity 18 TMB is a dual channel amp with Channel 1 – Tone and Volume, 2 inputs and Channel 2 – Treble, Midrange, Bass, Volume and Gain, 2 inputs. The tone controls are of standard Marshall “Tone Stack” design. The TMB channel incorporates a gain control and is a higher gain design similar to the Marshall 2203 of the late 70s. The master volume allows the player to selectively dial in overdrive distortion for that ‘crunchy’ Marshall sound.


The two channel Trinity 18 sIII is based on the TMB version. The sIII channel 2 also incorporates a gain control but gain is not as high affording some additional headroom. The sIII is voiced to sound like a vintage Marshall amp – JTM-45 Bluesbreaker style. Channel 1 is the same design as the original Marshall 18 Watt Tremolo channel. Channels can be jumped for even more complex sounds. This amp is great for reproducing the tones of the early Marshall years.


The Plexi design is voiced to sound period correct for a Marshall Plexi Lead. Screaming guitar lead tones at a much lower volume. The amp can thump and grind with less compressed tone than the other 18 watt variants. The normal Channel provides way more overdrive than most 18 watt normal channels while the Plexi channel is capable of the best clean sound we have ever heard come out of an 18 watter. With a pair of greenbacks, you’ll be shocked how period correct it sounds. Crank up the gain and you are in crunch tone heaven. The clean boost just adds another dimension, it nails all those old AC-DC tones dead on and has way more gain on tap if needed.

Plexi Mk II

The Plexi Mk II design is based on the Plexi Super Lead preamp design with selected “Brown” components. This gets you very close to Eddie van Halen sound. Hot licks but with a very surprising clean tone with gain turned down. This baby can move some real air moving! Crank up that normal channel and it really gives up the goods! Lot’s of crunchy to high gain AC/DC tones for days. The Plexi TMB side cranked up is equally 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 it up the TMB channel and just makes it a bit fuller spectrum of sound.
Plexi Mk II Clip by unimind


The v6 adds switchable output tubes and foot switchable boost. In this design, you can switch in 6V6 or the EL84 output tubes. The sound is close to a Fender Deluxe and an 18 watt grafted together.


Our Trinity 18 amplifiers are built using point-to-point wiring and turret board construction for service and reliability. High-quality tubes, coupling capacitors and resistors are selected for maximum tone, performance and reliability.

There are High and Low inputs for both channels.

The power transformer and output transformer are built to the original Marshall specifications and use vintage grade steel laminations.

The Marshall colour correct gold plexi front panel is painstakingly manufactured on Plexiglas using the original lamination process so it looks authentic and the chassis rear side is silk-screened. 


  • Channels: 2
  • Controls Ch.1: Volume; Tone
  • Controls Ch.2: Bass; Middle; Treble; Gain; Volume
  • Power output: 18 Watts
  • Preamp Tubes: 3-12AX7
  • Power Tubes: 2 – EL84
  • Rectifier: EZ81
  • Bias: Cathode
  • Choke: no
  • Speaker: per customer choice
  • Outputs: 2
  • Speaker Output: 4, 8, 16 switched
  • Voltage Support: 115 V 60Hz – 240 V 50Hz
  • Weight: Head: 20 lbs., 112 Combo 45 lbs.
  • Switches: Ch. 2 Boost; EL84 / 6V6 switch on v6 Model
  • Dimensions: Head: 8” H x 22” W x 8” D

Options included:

  • Piping: white, silver or gold piping
  • Tolex: black Mesa wrinkle, black, green, red, purple levant or black elephant
  • Grill Cloth: grey weave, Marshall black or salt & pepper, Fender silver, Ampeg black; Cane
  • Handle: strap style or comfortable leather “dog-bone” style
  • Knobs: choice of black or white “chicken head” style
  • Other Tolex, grill cloths and hardware are available and priced upon request.

Audio Samples

These clips were generously provided by Lawrence Bethune, Billy The Mountain and Gary Cox.

Once again, Lawrence Bethune played and recorded with the Trinity 18 for over a week and he has provided us with plenty of musical material to share. Listen to some samples below and we think you’ll be convinced!

Billy The Mountain is a band with the purpose of bringing the misfortune of others – children in particular – to global attention.

Hailing from the United Kingdom, Gary Cox, of The Gary Cox Band, is a renowned slide guitarist. Gary is playing a Lonestar Strat into the sIII amp through a 1×12″ Greenback and Shure SM57.

  1. Billy Beck - Bethune
  2. Summertime Billy - Bethune
  3. Back To The Billy - Bethune
  4. Rhumba Billy - Bethune
  5. Blue Billy - Bethune
  6. All Night Les - Bethune
  7. Stormy Monday - Bethune
  8. Strat Blue Sunday - Bethune
  9. sIII TMB channel Strat - Bethune
  10. sIII TMB channel Strat - Bethune
  11. sIII TMB channel 335 - Bethune
  12. sIII Normal channel on 10 335 - Bethune
  13. Plexi clip - Billy The Mountain's Nicolai Kehlet
  14. Trinity 18 Plexi-56 Les Paul - jonego
  15. Trinity 18 Plexi - Needham
  16. Billy The Mountain-Walk on Water
  17. Plexi Mk. II -Les Wilkins
  18. sIII Normal, tone 4, vol 4, humbucker - Cox
  19. sIII Normal, tone 4, vol 7, humbucker - Cox
  20. sIII Normal, tone 4, vol 10, humbucker - Cox
  21. sIII Normal, tone 4, vol 10, std - Cox
  22. sIII TMB, bass 5, mid 6, treble 7, vol 3, master vol 7, humbucker - Cox
  23. sIII TMB, bass 5, mid 6, treble 7, vol 7, master vol 7, humbucker - Cox
  24. sIII TMB, bass 5, mid 6, treble 7, vol 10, master vol 10, humbucker - Cox
  25. sIII TMB, bass 5, mid 6, treble 7, vol 10, master vol 10, std - Cox

Video Samples

Tone King Trinity Amplifiers Model SIII Review
Trinity 18 Watt sIII

Pricing Options

Canadian Customers
Click the 'Inquire' below to receive up-to-date Canadian Dollar pricing and shipping.
Trinity 18 Head sIII,TMB or Plexi
$1,260 USD
Trinity v6 Head
$1,360 USD
Trinity 18 1-12 Combo sIII, TMB or Plexi *No speaker
$1,410 USD
Trinity 18 1-12 Combo with Tone Tubby Alnico Red
$1,660 USD
Trinity 18 2-12 Combo sIII, TMB or Plexi *No speaker
$1,500 USD
Optional Voltage Regulator Module (VRM) - electronic attnenuator
$100 USD


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Payment Information

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.

We accept Canadian credit cards at our shop or by phone.

If you are located outside of Canada and want to make a payment using a VISA or Mastercard, an invoice will be provided using PayPal’s credit card service. No PayPal account is required.

Please be sure to send your full shipping address and contact phone number when ordering. If you have any questions, please contact us for more information, visit our web site or forum.

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