Mar 19

An intro to Eurorack modular synthesizers

An introduction to Eurorack Modulars


For sometime now I had been wanting to get myself a Eurorack modular synth but wasn’t fully versed in what I needed to actually make this happen. I was well aware of how one worked (this will be covered later) but not how to actually start without wasting a ton of money. I researched and patrolled forums, spoke to friends that owned modulars and generally took my time to make an educated decision on how to get my first system up and running.

Now I would like to pass some of that knowledge on. This article is intended to clear up some of the foggy entry points to Eurorack and make it a lot easier for people to get the systems they want at an affordable price. Please keep in mind because Eurorack Modulars are indeed fully modular, there is no one correct way to start your modular.

This intro video touches on a few of the topics covered here. I recommend watching it and reading the article as well.

What is a Eurorack Modular and why should I want one?

Eurorack is a modular synthesizer format, think of it like VST is a format for plug ins. Any module in Eurorack format can be placed into a Eurorack case (given you have the space and power allocation) and will work with other modules.  These modules range from basic  synthesis building blocks such as a Amplifier, mixer, Oscillator, envelope, filter etc. to more function and west coast school methods of synthesis such as Function generators (like the Make noise Maths) Flip flops, comparators, even digital control modules.  Eurorack allows you to configure a synthesizer with no set signal flow so that you can gain the most from the individual modular components. The benefits of this are you can do things many synths can not.  For example in most synths your VCO is limited as nothing more than a sound source. however with a  modular synth you can use a VCO to modulate other parameters, you can use it to trigger other modules on and off etc. Filters are no longer strictly for sound shaping and can be used to control pitch slew or even as gates. This sort of flexibility combined with the seemingly endless list of available modules provides for a supremely powerful platform to work in. Another great feature of modular synthesis is the idea of not only new modules and new companies coming up with great analog and digital sounding gear but also obtaining the sound of classic analog gear as well. Companies such as Harvestman, STG, Doepfer and more are creating new modules based on old classics such as Oberheim , Moog , EMS and vintage roland filters. There are even whole lines dedicated to recreating classic synths or our past. Combine those modules with the new feature packed and alternative modules of today and there really is no limit to what sounds you can achieve.

What are the basic components needed?


The first order of business is to understand what the bare minimum requirements are for a Eurorack modular. At the heart of any modular synth is the Case or Rack. Cases are measured in HP (horizontal pitch which is how wide your case and modules are), and the amount of rows are numbered in increments of 3U (a 9U case is 3 rows of Eurorack modules). Cases can come in many shapes and sizes. the Depth of the case can also be important as some modules are deeper than others. a Skiff case is a shallow case a Boat is a deeper case.  Many companies provide closable travel cases or bento box style cases. then there are wooden desk mount cases. again the shape and size depends on the manufacturer. the Lengths also can vary greatly. Many common lengths are 84hp, 104hp and 110hp.

The cost of these cases also can vary greatly ranging from DIY cheap to boutique sell your left eye for it cases.

on some cases power is integrated into the case, on some it is not. Here are some links to a few Case solutions that won’t break the bank. 6u powered portable BentoBox case = $375 , Control Voltage 9u wooden case = $325, Pittsburgh modular Cell 90 (3u) = $209

The Power

Power supplies can be a real scratching head point for many people trying to get started in Eurorack. In reality there are simply different entry levels to power supplies. While it is of course nice to have the best power supply that money can buy it is not a requirement. Quality linear power supplies can cut down on voltage fluctuations and cross talk or bleeding from one module to another. This will provide a more stable foundation for your modular system but also comes with a price tag. Another aspect to keep an eye on is whether you will need 5v power in addition to the standard 12v power. Often times digital modules will require this voltage source so if you plan on adding digital modules be sure that your power supply can handle it. A perfectly viable solution however is switching power supplies such as the TipTop audio Zeus  or even the TipTop audio uZeus power supplies. These are inexpensive perfectly good power supplies for most start up systems. There are also DIY solutions to build your own power supply such as the Synthrotek power supply.

Another thing to keep in mind when looking at power supplies is the power consumption of the system you are building. Most sites that sell eurorack modules will also list the current draw for each module. refer to the power supply specs  to see how much power your system will handle safely. Over shooting the power allotment can cause glitches in the system or even a power failure.

here are some links to some power solutions TipTop Audio Studio ZeusTiptop Audio uZeus

The Cables

The basic cables needed for a modular are standard 3.5mm or 1/8th inch mono audio cables. nothing special about them aside from the fact many people prefer to get different lengths and colors to aid in organization.  there are of course the higher quality cables that come at a premium such as TipTop stackcables which provide you with a open jack at the end of the cable allowing you to plug more than one cable into any jack. These are not needed but are certainly nice to have. I will cover more on this in the Multiples section.

The power cables are what provide power (and sometimes control voltage) between the modules and the power supply, these are often 10 pin to 16 pin ribbon cables with a red stripe indicating the common or negative wire.

Cables links TipTop stackcables (roughly $8 per cable plus shipping)  Erthanvar cables roughly $1.50 a cable but colored 

then of course you could always buy a large lot of 1/8″ to 1/8″ cables off of ebay or something but they tend to be long and look cluttered.


Modular synths are controlled by sending Voltage referred to as CV (control Voltage). This Voltage will control Pitch and also on off signals referred to as Gates or triggers.

The main modules you will need are first a way to control your synth. if you want a traditional keyboard way to play the modular you can start with something like a synth that has midi to CV such as the Microbrute or MiniBrute Synthesizer from Arturia as it has a built in midi to CV converter and can control a modular both from its key bed or and external source plugged into it. (there are a few synths out there capable of this today but I list those as they are the most affordable starting at only $299) Or you will need a CV keyboard or Midi to CV converter module.  another affordable and portable solution would be the new Qunexus which features CV outputs on it , or the Akai Maxx line of key controllers.




This is where the fun really starts.

Modules are the individual building blocks of your modular synth. By adding modules you will be able to create a synth that sounds and operates how you choose.  Modules come in a large variety of sizes and functionality from a myriad of different manufactures. At the end of this post I will list some of the more well respected manufactures and give links to some of these great modules. Remember modules are measured in HP (Horizontal Pitch) for the width. Each module will also draw current a typical specification would be something like this.

draw +12v: < 50ma
draw -12: < 5ma

this means the module is using up less than 50ma of positive voltage and less than 5ma of negative voltage

remember to add up all of your current draw for all of your modules to ensure your power supply can handle your draw.


VCO (Voltage controlled oscillator )-

This modules is essentially what produces sound. Voltage inputs are commonly

CV-Pitch, Sync (for having multiple VCO start in phase with each other), FM input , and PWM input (Pulse width Modulation input)

Different oscillators will have different characteristics. Some modules may have an odd shape to the triangle wave or maybe have interesting pulse width characteristics. Many of these modules vary in size but that does not mean a smaller module has a weaker sound. Looks can be deceiving sometimes.

How well VCO’s track refers to how well they stay in tune as you play notes up the keyboard. some VCOs might have an unruly character and only track a few octaves while others may be rock solid across 6+ octaves. Keep this in mind when selecting a VCO.

Outputs are commonly Waveform outputs such as square, saw,triangle. The outputs of these oscillators are always on so if you plugged the output directly to your mixer you would hear the oscillator and it would not stop.

This is why we use envelopes and amplifiers

Here are some VCO examples the Standard and Dual VCO units  Animodule LM-VCO  Intellijel Dixie II  Make Noise DPO Synthesis Technology E350 morphing terrarium (wavetable vco)

Slightly more odd VCO units Jupiter StormMutable instruments Braids  Synthesis Technology E340 cloud generator


The filter allows us to sculpt the sound of the VCO pretty straight forward as on most synths. Filters are commonly Low pass , high pass, notch, and band pass. Some inputs can be CV input for opening and closing filter, CV input for resonance, Pitch input for resonance key tracking, and of course audio input.

Filters can also be considered “low pass gates” and can involve features such as vactrol inputs which take a simple square or sharp on off signal and can round it out for a more pleasing sound.

Filters can also be used to shape control voltage as well. This can cause simple gates to act as more interesting rounded signals or pitch to have a slew.

Here are some great Filter modules STG sound labs Mankato , Animodule SOB FilterDinsync Sara VCF

VCA (voltage controlled amplifier)

the VCA is an important part of a modular system. this is what decides how loud a particular sound is and can be controlled from other sources.  A common usage would be to send a VCO into the VCA and have it controlled by a gate on off or envelope opening and closing. Also it can have more alternative sources such as LFO’s controlling a VCA to get tremolo or swelling effects. VCA’s can also be used to attenuate levels to match your needs.

Here are some VCA’s Animodule DD VCA , synthrotek MST dual VCA , Malekko VCA


Envelopes are a common building block and are used to decide how fast or slow a gate is used. when you press a key a gate is sent as an on signal (positive) when the key is released the gate is neutral the resulting wave on a scope would be a positive square wave. An Envelope can allow that immediate on off into a gradual on or gradual off. This is used to make more musical and pleasing on off note signals Attack Decay Sustain and Release are the common parameters.  Some envelopes also have looping features and can allow them to act as LFO modules.

Here are some nice envelopes Animodule Anvilope , Make Noise Function, Bubble sound DLADSR,  WMD multimode envelope


Low frequency oscillator is used as a modulation source. Think of them as a slow moving VCO that can be used to raise and lower other modules parameters. LFO common uses include being routed to a filter CV input to open and close a filter or to a VCA to create warbling or pulsing sounds. Wave shapes vary from LFO to LFO and can add variety to your sound. Many VCO can act as an LFO as well.

Here are some useful LFO modules 4MS pedals Quad pingable LFO, Doepfer A-146 LFO2Mutable instruments Tides


A mixer is just what it sounds like. A way to mix multiple signals into a single (and sometimes multiple) outputs. Use this to collect all of your VCO modules before sending into a filter. Mixers can also be used for control voltages to interesting effect as well.  Mixers can come in a variety of input and output configurations… not all mixers are the same!

Here are some Mixer modules Animodule Mixman , Doepfer A-138b mixerSteadyStateFate Mixmode


Multiples and buffered multiples are used to send single signals off to different sources. Think of it as a splitter. Buffered multiples prevent voltage drop from splitting off to to many destinations. Multiples can be easily built DIY projects or you can get them on the cheap. Buffered multiples tend to cost a tad more but are great for sending pitch out to many sources while keeping tune.

here are some multiples. synthrotek MST 07 Buff Mult , Animodule Line_Amp (line level to modular and buff multi)

Sample and hold

Sample and hold is a module that takes a fluid CV or audio source and turns it into a stepped output. the amount of steps is decided by a clock or pulse input. this can create some interesting effects such as bit reduction sounds, or jagged pulses.

Here are some S+H modules  Animodule ShNoizeSTG .shn

Effects modules

Just like a guitar pedal board, Euroracks can have many different effects. Effects can range from the standard spring reverbs and delays, off to the Control voltage effects such as stutters quantizers and retriggers. There are also CV effects such as gate delays, trigger offsets etc that will change the CV going into and out of the module.

Here are some FX modules Synthrotek EKO delayFlightofHarmony sound of shadows , Audio Damage Dub jr


One of the really interesting things about modulars is that you don’t have to use a traditional keyboard to play them. Eurorack has MANY sequencers and alternative input sources. Ranging from random voltage generating sequencers to deliberate step sequencers and everything in between. You might be surprised at some of the rhythms and melodies that can spring from these sorts of modules.

here are some cool sequencers Synthrotek Sequence 8, intellijel Metropolis , Make noise Rene, RYO VC sequencer


Many Modules have combined features to save space or just plain be more value per dollar and interesting.

here are some great combo modules Make noise Maths (multiple envelopes, LFO, slew, gate, clock super handy tool) Animodule Mixman (mixer, multiple, offset, inverter) Mutable Instruments Elements (a full modal synthesis engine)

RYO Optodist is a distortion/VCA


Putting it all together

Now that you Have selected what modules you would like to build up your modular synth it is time to install and put it all together.  The first thing to do is to install your power supply and connect each module’s power cable to the bus board. this will provide each module with the necessary power. This is a great time to decide just what you want the layout of your modular to be. Some people like to organize according to signal flow, some by module type. Once connected you can begin screwing the modules into place. It is often a good idea to purchase some nylon washers to go between the screws and the modules themselves to avoid “rack rash” or nicks in the metal from the screws.  After carefully connecting your modules and screwing them into place you are almost ready to go.



Signal Flow


What Modules to buy First


Tips and tricks patches


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