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Lummerland Express

Lummerland Express

Lummerland Express

The starter drug into the world of Lo-Watt Amps and at the same time the first project of the LoW series. But less watt does not necessarily mean that these amplifiers are less powerful.

Note: The first version of the Lummerland Express, further on called MkI, was released in 2013. The Mk2 version from 2020 is the current version and replaces the 2013 version. For the sake of completeness, the following text nevertheless includes both the Mk1 and Mk2 versions, as there are still numerous MK1 versions around.

The Lummerland-Express is based on Ken Fischer’s trainwrecks with the difference that the power amplifier does not use EL84s but double triodes, which are normally found in preamplifiers.

Besides the 12AU7 (Mk1) the Lummerland-Express also works with 12BH7 or ECC99 (Mk2) tubes without any problems. The 12AU7 or 12BH7 deliver a power around 1.5 Watt and the ECC99 deliver a power around 3.5 Watt. This may not sound like much, but it is not – and is often more than underestimated. To get an idea: the sound pressure level of guitar- and bass speakers is usually measured at a distance of 1 meter, with a power of 1 Watt and at 400 Hz and most of these speakers reach levels of 97, 98 or more dB – which certainly can't be called quiet.

The advantage of the Low-Watters from the LoW-Series is that you can crunk-up the power amp quite easily without the risk of a sudden deafness. Try this with a 100 W Plexi …

The circuit

As already mentioned in the beginning, the circuitry, especially the preamplifier, is clearly based on the Trainwrecks. But since the voltage and power basis is significantly different, several adjustments were necessary. Furthermore, the mid pot of the tone-stack was omitted and replaced by a fixed resistor, and the bass was reduced, because it was very dominant. To connect the preamp to the power amplifiers, further minor adjustments were necessary, which will not be discussed in detail here, as this would go beyond the scope of this text.

A significant change compared to the original is the phase inverter: the output stage of the “Lummerland” is powered by a “Cathodyne Phase Inverter”. This is a very minimalistic solution, because only one triode system of a 12AX7 has to be used for this, but more than sufficient for driving the power-tube of this amplifier. A “Master” in the output stage completes the overall signal concept and allows full overdriving of the preamplifier at low output power. Trainwreck fans might be a bit bothered by the Master, because the Original doesn't have a master either, but if you don't want one you can simply leave it out.

The output transformer used is a Hammond 125B which is connected with a Raa of 22k and therefore works with 12AU7, 12BH7 and ECC99 tubes. Even if there is a certain mismatch depending on the type of tube, this is not a disadvantage and does not matter.

A chassis especially designed for the LoW-Series can be used – unless you want to do the metalwork yourself. The components themselves are standard. The construction of the Mk1 was done in a kind of point-to-point and was replaced by a circuit board on the Mk2, which makes the build more easy, allows a stable mounting of the components, provides a fixed grounding and thus makes it less prone to errors – without any negative effect on the sound.

And the sound?

Finally, the mother of all amplifier questions:
What does the Lummerland Express sound like? — Well, Good! ;-)

Sound is difficult to describe because it is subjective and influenced by numerous factors. The Lummerland Express is not a Bassman ultralinear clean amp. It definitely can't do that at all, and that wasn't the goal of this amplifier. Even though it reacts very well to the volume pot of the guitar and can be played almost “clean”, there is always a certain amount of overdrive. The real joy of playing comes when the gain is on the far right, just like the master, and a guitar with powerful humbuckers is used. This combination will result in a full and warm Rock to 80s Metal sound with tight bass and a smooth top end. All in all, a real Rock-Amp.

Files

Mk2 version from 20. August 2020
Schematic and Layout Mk2 as PDF

Mk1 version until 20 August 2020Discontinued!
Schematic Lumex MK1 as PDF

Layout Lumex MK1 as PDF

Mods

For some people, the Lummerland sounds too smooth and somewhat undefined at the low end. As a remedy just replace these components / values:

  • R6: 6,8 kOhm
  • C5: 1 nF

Media

Sound Demo 1 (YouTube)

Sound Demo 2 (YouTube)

Sound Demo 3 (YouTube)

Components

A kit with components, the matching chassis (which works well for other projects of this type too), and face plates are available in the TT-Shop

Warning!

Care is necessary during construction! Even though this is a low-watt amp, the voltages used are potentially fatal. The Lummerland 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.

Pictures of the Mk2 version

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