TT 18 Watt

Traditional point-to-point assembly, clearly arranged with simple circuitry and warm and pleasant tube sound - it is no coincidence that the Marshall 18-Watt is one of the most popular amplifiers in the DIY-scene.

Despite the fact that many assembly kits for amplifiers already exist on the market, we have decided to create an assembly kit, so that we can ensure the best possible selection of the individual components to each one another and create a final product, which will satisfy all the wishes of the customer and may even be better than the original.

Tremolo

The tremolo channel in the 18-Watt model is well-known for its background noise. And this topic has been hotly debated in various forums. In order to reduce and suppress this background noise, we have made some changes in the area of the tremolo and implemented them as follows:

Better filter for the output of the oscillator stage by increasing the capacity of the capacitor C14 from 0.047 µF to 0.1 µF
Since the capacity of the foot switch cable was part of the original circuit, and problems with oscillations may occur without a connected foot switch, we have inserted a capacitor which can replace the capacity of the foot switch when it is not being used. (C20, see schematic)
Slight adjustment to the oscillation frequency by reducing the resistance R27 to 680 kOhm (see circuit diagram). The frequency range of the tremolo can be lowered somewhat if a 1 MOhm resistance is used at this position if a “slower” tremolo is preferred

Voltage

Adjustment of the resistance in the voltage supply to current 18-Watt transformers by increasing the resistance values of R16, R17, and R32.

The chassis used was developed on the basis of the standard 18-Watt chassis and expanded with additional cut-outs for the installation of one of the TT Effect loops. In our opinion, this represents a sensible addition to the amplifier.

In all other respects, we kept as closely as possible to the original circuitry and component specifications with regard to design and assembly of the kit.

Files

Shematic as PDF (2 Pages, DIN A4)

Layout as PDF (1 Page, DIN A3)

Misc

Posting from the TT Forum about building the 18 Watt with an FX-Loop and some other mods.

Sound-Demo 18-Watt (YouTube video)

Components

You can order the 18 Watt Kit and many other items in the TT-Shop

Warning!

Care is necessary during construction! Even though this is a low-watt amp, the voltages used are potentially fatal. This amp is NOT a beginner's project!

A successful build requires that you can read (and understand!) a schematic diagram, you know how to use various measuring devices, and you have some experience working with voltages over 60V.