Modular synth components

Martin McBride, 2020-08-05
Tags modular synth components sound synthesis
Categories computer music sound synthesis modular synth

Modular synthesisers are made up of separate components that you can either buy or build yourself. You can generally mix and match components from different manufacturers, and any you build yourself, because they are all built to certain standards which specify their physical size and electrical connections.

In this section we will look at some common types of module, and describe what they do.

Basic set up

The simplest modular synth that can create any kind of sound will normally require, at least:

  • A rack, which is often an open fronted box that houses the modules.
  • A power supply.
  • Some kind of speaker or headphones.
  • An oscillator.

But that would be pretty boring, it would just play one continuous note that you might be able to change by turning a knob. In order to create anything resembling music you would need:

  • A simple sequencer to play a sequence of notes.
  • An envelope generator.

A more usable setup would normally have:

  • Multiple oscillators, so you can have several layers to your music. Typically you would have different types of oscillators, that each create their own different sounds.
  • A mixer, to combine several sounds.
  • Several sequencers, perhaps including an arpeggiator that automatically plays note sequences, and a drum sequencer (plus a drum symthesiser) for adding a drum track.
  • A midi input so you can play the synth with a keyboard.

Common effects you might add are:

  • A low frequency oscillator to create tremolo, vibrato and pass effects.
  • Filters to change the timbre of the sound.
  • Echo, chorus and reverb effects

There are also all sorts of weird and wonderful special modules for creating other effects.

The rest of this chapter gives and overview of the different components.


There are several different modular synth systems. The system defines the physical size of the modules, the power voltages, and the types of connector used for interconnecting modules.

We will only discuss the Eurorack system, as it is probably the most popular.

Eurorack specifies:

  • The front panel size of a module is 128.5 mm high. The width of a panel can vary, but it must be a multiple of 5.08 mm (which is exactly 0.2 inches). This width is called the horizontal pitch or HP. For example a 3HP module is 15.25 mm (0.6 inches) wide. Different modules have different widths because some modules have a lot more sockets and control knobs than others.
  • The power supply provides +/-12V plus an optional +5V supply. In other words it has 4 rails: +12V, +5V, 0V, -12V.
  • Patch cables are 3.5mm mono jacks.

Here is a typical module:

And here is a typical patch cable:


Here is a commercially available Eurorack rack. The modules are fitted onto the rails, and the power connector is inside the box. This allows you to mix and match different module (they should all be the Eurorack standard height so they will fit the rack):

Racks can be quite expensive, and it is not too difficult to build your own if you want to save money when you get started. At the most basic, you just need a simple wooden frame or open fronted box of the correct size.

If you really want to put the effort in, and your wood working skills permit it, you can make a good quality box out of decent hardwood, and polish it. You will end up with something that is better than anything you can buy.

You can also make the rack out of metal if you prefer. Some people choose a more original option, for example it is possble to create a rack built into a suitcase, which is great for portability.

To be continued.