CTA Classroom: Using Auxes, Groups, VCAs & Matrixes Pt. 4

We’re finally wrapping up our tour of the alternate ways we can mix a signal. Last time, we dealt with the aux and group layers, today we’ll key in on VCAs and the matrix mix.

Using VCAs

VCAs, as we mentioned before, are basically remote controls for your faders. You can assign a collection of faders to a VCA and then control the level of all of those faders using a single VCA. I use VCAs for giving me a way to control the overall mix of the band on a few faders. In our setup, we have drums, guitars, keys, perc or winds (depending on the week), BGVs and wedges. A couple of notes.

Some like to put the bass into the drum VCA, and there’s good reason to do so. I don’t because I have enough faders to do most of my mixing on channel faders. It’s a preference thing and you can try it both ways to see what works best. I also use a VCA for my wedges because I can. By assigning the aux masters that I use for monitors to a VCA, I can keep those aux masters on another layer out of my way and turn all four monitors on and off with a single fader.

 

This is just one of the many ways to lay out your VCAs. Image courtesy of APB Dynasonics

I’ve also created a single band VCA in the past that controlled all instrument and vocal inputs. I didn’t use it for mixing, but for taking the entire band out in one button press (on that desk, a VCA mute muted all the channels, including monitors). I still had my individual VCAs as well, and I did some mixing on them. 

Any time you want to control a group of inputs as a whole, a VCA is a great way to go. Drums are a perfect example because once you get the various drum mic's dialed in and sounding like a kit, you typically want to raise and lower the level of the drums, not the toms and hat (well sometimes you do…). The VCA will maintain the relative mix balance between the channels but give you “master” volume control over all of them. 

Background vocals are similar. Get your blend set up correctly, then mix them with a single fader. Once you see what you can do with them, possibilities abound. 

Using the Matrix

For a novice sound engineer, a matrix mix can be really confusing. I remember years ago encountering my first matrix mix. It was at a large church, and they mixed on a large analog console. In that case, they used the matrix to balance out the relative levels between the main speakers and the downfills. When the tech guy showed me that system, I asked, “OK, but how do the signals get into the matrix.” His reply was, “You just turn these knobs up.” 

I knew that. What I didn’t know was the source of those knobs. Apparently he didn’t either because he never did answer me. I finally resorted to the manual and learned it wasn’t that mysterious. 

As I mentioned in the descriptive post on the matrix, modern digital consoles have blurred the definition of a matrix. On many consoles, they can be used like auxes, in that you can send any or all channels to a matrix mix. Other consoles only let you send the groups there, perhaps with some limited number of channels.

The columns are the inputs into the matrix, the rows are the individual matrix mixes. I use this to level-balance the band and speaking mic's, build lobby and video mixes, and drive the FOH Buttkicker.

So what do we use them for? Well, in our church, I use them for sending mixes to various outboard locations; video, CD, 2-track board mix, lobby, cry room, things like that. I use my aforementioned grouping system to balance out the levels, then use eight of my twelve matrix mixes for driving those destinations.

Sometimes, you just need a spare mix for something, but don’t want to burn an aux or a group. I use a matrix for driving my butt kicker up at FOH. It’s driven by a single input—my sub aux—but by passing it through a matrix, I can set the delay for FOH and have an easy, single-fader control for level in the booth.

I also use a matrix mix for my FFT analyzer. By putting both L&R into a mono matrix, it combines them and makes it easy to compare the output of the desk to the measurement mic. This allows me to pad the level down so it matches up properly in my audio interface.

Uses for a matrix are really limited only by your imagination. Just don’t overcomplicate the system just so you can use all your matrix mixes. Remember, the goal is not to use 100% of the capabilities of the board just because you can. We use these tools to make life easier and get done what we need to.

And that’s the goal of this whole series; to give you ideas on how to use the tools you have to the greatest good. Now go read your manual and come up with some better routing ideas...

As we wrap up, I want to link to ABP-Dynasonics. Not only do they make great analog consoles, they also have some of the nicest drawings of those consoles on the web. I'm thankful they are available as they make great reference pictures. I reviewed a ProDesk 4 a while back; it's a great mid-priced analog console.

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