It’s an age-old question, and it’s one of the most common questions that I get from audio students. “Do you use VCAs or subgroups? How are they different, and what are they used for?” I usually try to start right off by answering that it’s a false question. VCAs and subgroups (often referred to simply as “groups”) are two totally different tools, and they shouldn’t be compared to one another. For the most part, that’s a true statement, but like anything about audio, the real, in-depth answer is nuanced.
DCAs and VCAs
Although different in design, from the user perspective, DCAs (Digitally Controlled Amplifiers) essentially function identically to VCAs (Voltage Controlled Amplifiers). Here, for simplicity, we’ll use the term VCAs for both.
At the same time, VCAs and subgroups — while different — are often used in conjunction with one another. I would consider myself a die-hard VCA mixer and a die-hard group mixer. I rely on both of them heavily, especially for the type of mixing work that I do.
Groups and Auxes
It can’t hurt to provide a brief explanation of what a group actually does, and this is another common discussion between my students and I. When input channels are assigned to a subgroup, the send to the group is post-fader and unity gain. That means the position of the input channel fader directly controls how much level goes to the group. The follow-up question often centers around how that differs from an aux. While an aux can be used to achieve the same thing as a group (by setting its send to 0 dB and making the send post-fader), the differentiating factor between a group and an aux is the send level control itself. Groups don’t have sends, they pick off their signal from the input channel, post-fader. Auxes have sends (typically a rotary level control), and the sends can be set to pre- or post-fader.
Subgroups
I only use subgroups for one thing — group processing. I honestly can’t see another reason for using them in a live mix, assuming a console has VCAs and groups. Certainly there are all sorts of utility reasons to use subgroups. For example, groups might be used for recording stems, but from a purely live mixing perspective, group processing is what it’s all about. Group processing techniques such as group EQ or parallel compression are an entire article unto themselves, so I’ll leave that alone for now.
VCAs
On the other hand, VCAs are just a remote control for other faders. The analogy I often use compares VCAs to the remote control for a television. When you’re sitting on your couch, turning the volume up or down on your TV, the sound from the TV isn’t routed to the remote control. The remote control is simply telling the TV to “turn up” or “turn down.” That’s what a VCA does. No audio is routed to the VCA, and therefore no processing can be done to a VCA, and a VCA can’t be assigned to your stereo bus. A VCA acts as a remote trim control, boosting or cutting the level of assigned faders relative to their current position. Historically, VCAs have been used to control input channel faders, but in the age of digital consoles, a VCA can be freely assigned to control input channels or output bus masters, or any combination thereof.
VCAs and Subgroups In Practice
To answer that age-old question of “Which do you prefer, VCAs or groups?” my reply — of course — is both! They are such completely different mixing tools that I can’t imagine mixing without them. The reality is that I’m always using subgroups and VCAs in conjunction with one another.
Let’s look at a very common scenario with drums, although the same can be applied to vocals, choir or virtually any other set of like instrumentation/sources.
First, I start by assigning drums to a stereo subgroup. I rarely use mono subgroups, because most of the time I need panning capabilities on the inputs that I’m grouping. Next, I’m going to set up processing as needed on my group. This often consists of a few plug-ins for overall EQ and compression, but it could be lots of different things depending on the contents of the group. Once my group processing has been set up, I then assign the group’s master faders to a VCA. Why? Because during a service, I want to be able to live on my VCA bank, rather than having to flip back and forth to and from my groups. In fact, my group masters never leave unity. Instead, I use VCAs to control the level of the groups making it to the stereo bus. Also, I never assign input channels directly to a VCA if they are feeding a group. That’s an important distinction. If input channels are being directly controlled by a VCA, any level adjustment of that VCA changes my send level to the group, which renders my group processing useless. The key to this technique is to keep a relatively constant level going into the group, and then use the VCAs to control the level of that group in the overall mix.
At the end of the day, there are very few things in audio that represent the “right way” to do things. Everyone has their own approach to mixing, and these techniques may or may not work for you. It’s up to each individual to develop their own approach by learning from their mentors and developing new techniques. That’s what makes every audio engineer unique and allows us to keep pushing the boundaries of audio further.
Vince Lepore is the technical director at St. Luke’s United Methodist Church in Orlando and teaches live production at Full Sail University.
