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Trinity 18 Watt Overview

The Trinity 18 uses a pair or EL-84 output tubes, 3 12AX7 preamps, and an EZ-81 rectifier.  It is a Cathode Bias, Class AB all-tube design using a tube rectifier.  Original spec power and output transformers are used exclusively.

The amplifier does away with controlled or corrective 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.

TMB - 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.

sIII - 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 jumpered for even more complex sounds. This amp is great for reproducing the tones of the early Marshall years.

Plexi - 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 new 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:

v6 - The v6 adds foot 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.

The 1X12 model weighs in at a healthy 45 pounds.

Product Specs

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

Trinity Amps builds five Trinity 18 amplifier versions based on the original Marshall 18 design. The Trinity 18 sIII, 18 TMB, Plexi, Plexi MkII and v6 all with Treble-Midrange-Bass, Gain and Volume.  The power transformer and output transformer are built to the original Marshall specifications and used vintage grade steel laminations.

When you purchase a Trinity 18, several options are included in the price:

  • Piping: White, silver or Gold
  • Tolex Covering: Black, Green, Red, White or Purple levant or Black Elephant, Black Mesa Wrinkle
  • Grill Cloth: Marshall Salt & Pepper,Bluesbreaker, Fender Silver, Grey Weave
  • Handle:  Marshall Strap chrome or comfortable Leather “Dog-Bone” style handle

Other Tolex, grill cloths and hardware are available and priced upon request.

The 1X12 Combo weighs 45 pounds and the head version weighs 25 pounds.


  • Trinity 18 Head sIII,TMB or Plexi....................................................... $1200
  • Trinity v6 Head ................................................................................... $1300
  • Trinity 18 1-12 Combo sIII, TMB or Plexi (no speaker)................... $1350
  • Trinity 18 1-12 Combo with Tone Tubby Alnico Red .................... $1600
  • Trinity 18 2-12 Combo sIII, TMB or Plexi(no speaker)....................... $1400
  • Optional footswitch controlled electronic 'soft switch' boost ............. $100
  • Optional Voltage Regulator Module (VRM) - electronic attnenuator ...... $100
  • Click here for Trinity 18 Watt Kit Info

What You Should Know About Pricing

  • All of our products are created using the quality parts you would expect in a great sounding amplifier.  A comprehensive user manual including amplifier operation and maintenance, circuit descriptions, tone tweaks, schematic and layout is provided with every purchase.
  • Trinity Amps recommends Tone Tubby Loudspeakers but you can install others as desired.  This allows you the freedom to select a driver for the specific tone you desire.  We will install them for you at no extra charge, or you can install them yourself.
  • All listed prices are in US dollars. Shipping from Toronto, Canada and applicable taxes not included. Specifications and prices subject to change without notice

How Does it Sound?

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