I was lounging at the console of a recent gig with my business partner and good friend Gordon Wood. He runs Zeitgeist Audio in the Buffalo, NY area and while we sometimes get to team up and tackle a big event together, he mostly handles all the events that I can no longer do because I'm mixing weekend services at my day job. At any rate VCAs aren't a part of his daily routine and since they are very much a part of mine he asked if I'd do a post on them.
A VCA is a voltage controlled amplifier. Which sounds weird because to look at on a console you would think "fader" would be a more accurate description. Generally they're a group of faders in the output section of a desk that you can set up to use as remote controls for other faders.
"Why wouldn't you just do that on the groups?" you ask.
Well, you may want to have group control over a set of faders but not necessarily have that signal travel through additional pathways to do so. Sending your drum channels to a group is a great way to remote control them and it's the only way if your console doesn't have VCAs. But using a group means that those channels are routed through additional gain stages where you have the opportunity to insert outboard gear. If you don't need to do that, why put your signal through all that? When you assign channels to a VCA their routing can stay the same and be as direct as you want it to be.
There are different things you can do with VCAs too. My daily driver is a Midas Legend 3000 which is a dual purpose live console that has some special features to allow for easier monitor mixing from front of house. So not only can I assign a group of choir mics to a VCA to run them up and down while keeping their balance the same, I can use a second VCA to control their level in all the monitor mixes. Other consoles, especially digital ones have all sorts of options you can get into. I think some of the bigger Midas ones will actually allow you to control the strength of your coffee with one.
Something else I do with mine is to simply remote control all my playback channels. I like to stay right at the center of the mix so I can be close to all my most important channels. If I need to touch the drum mix I have to take a step to the left and if the playback needs adjusting a step to the right. But since I only ever have one machine playing back at a given time, all eight channels can stay at unity on the faders and I can mix whatever happens to be playing back with just one and it's right in the center where I am, no stretching.
On the digi desks, it can make a guy nervous to flip through pages of inputs and not have instant access to important channels. When I was trying out a Soundcraft Si3 I assigned a VCA to the lead vocalist and another one to the pastor, as well as all the usual suspects like drum and key groups. That way if I happened to decide to tweak some far flung channel during the sermon I could still grab the pastor's mic in a hurry, without having to remember which page his input was on.
So my Brethren of the Knob and Fader, fear not the VCA, it is your friend. Anyone got useful tips or ideas about VCAs that I left out? Hit the comment section.