Synthrotek DIRT Eurorack Module - DIY Build

Completed DIRT Module
Completed DIRT Module

A classic Synthrotek filter, the DIRT is a 4HP module that is a necessity in any modular system. We actually have two of these and forgot to do a build video for the first… so guess what we did? You got it, a time lapse build of our second little module with grit.

What is the Synthrotek DIRT? It is described as a low-pass filter or effect module for eurorack modular systems. It has three knobs all which coinside with different variables of tone/sound. It can be used for filtering, ring mod effects, wave shaping and even harmonic distortion (which you can hear in our audio samples below).

Let’s get on with the build shall we?

How hard was the build?

The Synthrotek DIRT is a pretty simple build actually. It took about an hour to complete with a few stops along the way to change the tunes and grab some knobs for customization. 

One thing you want to make sure to pay attention to is the polarity of the caps (as usual) and the values of the potentiometers. There are only three pots, but all three have different values. The nice thing is that Synthrotek provides a great assembly guide and packed BOM for your reference. When referring to the assembly instructions, you will find that there are actually three different versions of the Synthrotek DIRT. A 9V standalone version (for pedals) and 2 eurorack versions are available. (At the time of this review, PCB version 2.2 is the current version). 

DIRT Time Lapse Build Vid

Play Video

When we started the build of this module, we decided to do a few top-down soldering points on the resistors and diodes. This was to just help hold things in place as we flipped the PCB over. Upon flipping the board over, you have to make sure to keep your iron hot and watch for bridges due to some close soldering points. 

Since the build only took about an hour (along with breaks to change the music and grab some quality H20), we found ourselves wrapping things up before we knew it. The three pots are all different value, so make sure to double check before tacking them down.

Pro Tip: Place a little solder on a pad, then hold the component where it goes while heating up the other side of the pad. By doing this, you can just push the part through the PCB, instantly tacking it in place. (You can easily burn yourself doing this if you are not careful).

Synthrotek DIRT Build Gallery

In our sample videos below, we started with the basic sounds of the fiter/effect. You can tell there isn’t a lot of “gusto” by itself but once you start patching with the Synthrotek DIRT, things quickly become layered and tormented.

Our first video has us patching internally on a small rack, whereas the second audio sample vid shows us patching through and into a Behringer Neutron. Oscillators from the Neutron mixed with the chaos from the DIRT created an atmospheric sound that really stuck with us. As you can see from the video, we continue to develop this sound throughout the rest of the video. Good stuff!

DIRT Audio Sample Vids

Play Video
Play Video

Module Control and Specifications



– CUTOFF = Cutoff Frequency

– RESONANCE = Increase the Q!

– BIAS = Set the bias correctly or not, the choice is yours


– PCB Dimensions: 4 x 1.5 inches

– 4HP

– Power consumption: >1mA

– Input, Output and CV Jacks (version 2.2)

DIRT Purchasing Links

Fully Assembled DIRT

Click the image to the left to be redirected to the Synthrotek Store page to purchase

  • Completed Module – ready to rock!
  • Price: $64.99
  • Part No: C-M-DF
  • Schematic

DIY Eurorack Kit

Click the image to the left to be redirected to the Synthrotek Store page to purchase

Panel and PCB

Click the image to the left to be redirected to the Synthrotek Store page to purchase

Our Final Thoughts . . .

The Synthrotek DIRT is a great filter. We happened to have two thanks to a sale giveaway that the gang at SR were offering. Why not have 2? We have multiple modular systems and having a DIRT in each one doesn’t seem off by any means.

The little 4HP module packs a punch and it can add another layer to your modular performance. With its low price and expansive filtering abilities, everyone should have one of these in their rack!

If you have questions about the build process or suggestions/feedback about this article, feel free to let us know by contacting us  We look forward to hearing from you!

Until the next build … 

~ f i N