Modular Synthesis 101 – Part 1

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This is my first post in a planned series on modular synthesis. Over the course of the series I hope to provide an introduction to the basics of modular synthesizers and take a look at some of the specific modules available in the increasingly popular Eurorack format. I am by no means an expert on the subject but believe I know enough to hopefully provide a place for beginners to learn the fundamentals. I will rely on the critical feedback of my learned readers to kindly point out any inaccuracies I may inadvertently include in my posts but I’ll try and keep the need for that to a minimum.

In todays post I am going to introduce some of the various modular synthesizer formats and define some of the basic terminology. In later posts I will dive deeper into the different modules, their functions and some of their uses.

The first thing to know about modern modular synthesizer systems is that there are several formats including Euro (or Eurorack), Frac (or Fracrack), Buchla, Serge, MOTM and several others besides. Some of the things that may differ between the formats are the height of the modules, the supply voltages, the power connector type, the mounting hardware and the size of patch cables used. The format that is arguably the most popular right now is the Eurorack format and that is what I will focus on for this series.

Eurorack modules are 3U in height, which is to say that they are roughly the height of three vertical pieces of rack gear in a standard 19″ rack. Though 3U is technically 5.25″ or 133.35mm, Eurorack modules are usually 5mm shorter than that, but we still call it 3U.

The other measurement you will hear a lot with Eurorack modules is “HP” (horizontal pitch) or less commonly “TE” both of which are a measurement of the width of the module where 1HP (or 1TE) is 5.08mm, or 1/5″. The smallest modules are typically 2HP and modules are usually multiples of 2; so 4HP, 6HP, 8HP, 10HP and so on.

Of course to use modules you will need a case (with a power supply) to put them in. Many options are available. You could make a case yourself, purchase a full case from one of the several modular case manufacturers such as Monorocket, or get a kind of in between solution that is great for beginners such as the Tiptop Audio Happy Ending Kit. Cases are always at least 3U in height and are then in multiples of 3U thereafter. Widths vary but 84HP – 90HP are very common widths for cases. I’d recommend making sure the power supply in your case has both +12/-12V and 5VDC output but this should be true of most case power supplies.

Eurorack modules use +/-12VDC or 5VDC for power and usually connect to the power supply by a ribbon cable and a common 12 pin connector. It is very important that the connector be oriented correctly. Usually there is a red stripe on the ribbon cable that indicates the -12V side of the connector. Connecting an incorrectly oriented power connector to a Eurorack module and turning on the power can damage or destroy the module.

Eurorack modules use 1/8″ (3.5mm) mono connectors and plugs for patching. There are many different lengths and colours of patch cables available today, one of the more popular ones being the Tiptop Audio StackCable which allows you to connect your cables to each other, or “mult” them in the modular terminology. This allows you to for example take multiple outputs from one jack on a module or to combine signals going into an input.

Mentioning stack cables I feel I should add a caveat that may be a bit confusing for new comers to modulars or electronics. Feel free to skip this part for now or just don’t worry if you don’t get everything I am discussing.

There are several important things to be aware of when using stack cables or any passive multiple, rather than a buffered multiple. A multiple in modular land is just something that lets you split (or combine) a signal. A passive one, such as when stacking cables like this or using a passive multiple module simply provides a direct connection between the cables. A buffered multiple would buffer the signal so that the same signal would come out of each output connected to the mult.

If you split a signal output you will potentially have a lower current flowing through each of the cables depending on the input impedance of the inputs your cables are plugged into. This isn’t necessarily a bad thing but depending on what you are doing you may not have enough input current to trigger or effect the module whose input you are plugged into.

Of greater concern is combining signals at an input. It is generally a bad idea, unless you really know what you are doing, to combine inputs passively, such as using stack cables. The reason is that you can very easily exceed the tolerance of the input to the module that you are combining signals in to and damage your module. If you want to combine signals you should use a mixer of some sort so that you can reduce the level of the various signals to make sure the total signal you are passing to your module is at a safe level.

I hope you have found this tutorial useful. I know some of this stuff seemed confusing when I was first getting into modulars. Next time we will start in on the basic modules and concepts of connecting them.

Happy patching!

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About jjob

I'm a technologist and a music producer. I make sound, write code and build things with electronics and microcontrollers.
This entry was posted in Eurorack, instrument, MIDI, modular, sound, Synth and tagged , , , , , . Bookmark the permalink.

9 Responses to Modular Synthesis 101 – Part 1

  1. Chad says:

    I’m thinking about building a Eurorack this year. This is great, thanks.

  2. Tim says:

    Cheers for this jjob. I’ve been wandering into modular synths for quite a while now and am almost at the point where I’ve convinced myself to get one. The 3RU thing was new to me. So for example, I have a 6RU 19″ rack case. How many HP wide is it? Looking forward to more posts.

  3. It’s really a nice post for the people like me who is looking forward to get in to #Modular so please keep posting :)

  4. Drew says:

    Hey, thanks for your post. I have a quick, specific question for you. I am looking to start a small modular set up with mutable instruments braids as the first piece. In addition to a midi to cv converter (I will initially be sequencing with my dsi tempest), what else do I NEED to get a line level audio signal to my mixer? That is to say, besides a powered case, what to I need to plan on purchasing before I can even get a functioning set up? A VCA is necessary I presume? Thanks

    • jjob says:

      You should be able to run the output of the Braids into a mixer without any problem as modular signal levels are quite high, however without a VCA and some envelopes you will just get a steady sound from the Braids. You likely want to use the gate out of your MIDI to CV to trigger an envelope which would control the VCA so that you can get more than just a drone from your oscillator.

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