Welcome back to Getting Started, the series where we explore the fundamental types of Eurorack modules and discuss what they do, how to use them, and how they fit into a system. Today, we’ll be discussing a few types of audio mixing, and how to get sound out of your system and into the world. 

Audio mixers: the basics

Mixers are an important utility: traditional mixing consoles are a key part of recorded music, and in modular, mixers offer an even wider variety of uses in a modular system. 

The concept behind a mixer is simple: two or more signals are mixed into a single signal. Features vary greatly from module to module, so we’ll go over some common types and you can pick the ones that fit best into your system. 

Some Eurorack mixers can also be used to mix CV: in this post we’ll be focusing on audio mixers, but check out our previous post in this series to learn about CV mixing, too!

Mixers for sound design

The simplest mixers have a number of inputs, and an output. These are known as unity mixers and don’t offer any control over the levels of individual signals; these can be useful for simple tasks like mixing multiple drum voices. Slightly more complex mixers will offer level controls per channel, so that a balance can be created between all the mixed elements. Usually, they will also be mono: that is, they have only a single output. While small, utilitarian mixers may seem unexciting at first glance, they open up a lot of possibilities.

It’s quite common to use a simple mixer like this to combine multiple signals together in the sound-design process. A famous example of this is Moog Model D: its 3 oscillators are mixed together, then run through a filter to shape their tone.

I use quite a few mixers when I’m working on percussion patches: it’s quite common to mix noise with a modulated oscillator when creating snares, for example. 

Small submixers like this come in a variety of form factors. There are a number of extremely simple mixers, such as the Bastl ABC, that work quite well in this context. Many multi-channel VCAs can also mix their channels together, so you may have a small mixer already in your rack. 

Mixers for arranging and performing

If your Eurorack system only has a single voice, you probably don’t need a large mixer. However, if your system expands to have multiple voices, or something like a percussion section, larger mixers become quite helpful for arranging a song, performing, and creating the right balance between elements. It’s common for this style of mixer to have 6 or more channels, and a variety of other features, which becomes quite useful in large patches.

Channel controls

Similar to small mixers, large mixers will usually have level controls per channel. They’ll often include pan controls per channel as well, as many large mixers operate in stereo: pan controls let you change the placement of a sound in the stereo field, from left to right. 

Some will have channels that have two inputs to take in stereo signals, and others will only have mono inputs that can be panned.

CV control

Some mixers also feature CV control over level and panning of channels. This can be a useful way to bring a mix to life; modulating the pan of multiple channels with slow LFOs is one of my favorite techniques for creating movement in a slower patch. 

Outboard mixers

If an in-the-rack solution takes too much space, a standalone mixer can be a good choice, especially if you have other instruments in your studio. Standalone mixers won’t have Eurorack-specific options like CV control, but generally they’ll take Eurorack-level signals just fine, and work great for leveling and panning. 

For advanced patchers: aux loops

Some large mixers have aux channels that can be used for routing multiple elements of a mix through a single effect. Each aux channel will have an output and an input. A common use is with reverb: the aux output goes to the reverb input, and the output of the reverb goes to the aux input on the mixer. 

The aux output on a mixer is effectively another small mixer: each channel will have an aux send parameter that turns up the volume of that channel on the aux output. 

Setting up an aux loop is simple: patch the ins and outs as described above, and set your reverb’s wet/dry mix to 100% wet. The main mix acts as the dry part of the signal, so we only need the processed sound in the aux loop. 

Of course, many types of effects can be used in aux loops: delays and compressors are commonly used in traditional mixing, and we’ve heard some awesome patches using distortion modules patched into aux loops. 

WHAT ARE SOME EXAMPLES OF MIXERS?

Here are just a few modules that can perform some of the functions we've been chatting about. There are always lots of choices in modular!

WMD Performance Mixer: An 8-channel CV-controllable mixer with lots of features designed for performance. 

SSF Vortices: A patchable mixer with a tape-inspired sound.  

Qu-Bit Mixology: A four-channel CV-controllable mixer.  

Intellijel Mixup: A small stereo mixer with some useful performance features.  

Bastl ABC: A 6-input mixer that can be used for mono or stereo applications.