The Difference Between VCA and Sub-Groups in Mixing

VCAs and sub-group busses can be easily confused. Here’s your primer on the difference and 

when it makes sense to use one vs. the other.

As you probably know from the way audio signal flows through a sound console (analog or digital), every single channel strip on a mixing board has an output that can be assigned somewhere. By default, all channels output to the stereo output—meaning all the individual channels are mixed down to a single stereo channel pair, which sends the music to your left and right speakers or headphones. Let's take a look at how sub-groups and VCAs alter the audio flow and how you can use that to your advantage.

What is a VCA in audio mixing?

In technical terms, a VCA, or Voltage Controlled Amplifier, is an amplifier that modifies its gain depending on a control voltage. If your eyes widened and none of that made sense, don't worry. It's a bit confusing, so let me try to explain that in a more human format.

VCAs were first introduced on high-end live mixing boards, particularly in larger productions. Nowadays, they're used everywhere⁠—from every Broadway show to home studio productions in your DAW.

A VCA group allows you to control the volume of multiple channels using one fader, without changing their routing. Imagine this scenario⁠—you have a great mix for a song, but you realize that as much as all your drum tracks sound perfect together when you solo them, collectively the drums in context are too loud. You could manually drag down all the faders for each drum channel by the same amount, but that's a lot of work. What's worse, you risk accidentally slightly altering the balance ratio between the different drum elements. This is where a VCA can come in to help.