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Author Topic: DCA/VCA & Matrix explanation  (Read 36938 times)

Kristian Stevenson

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DCA/VCA & Matrix explanation
« on: April 27, 2010, 12:41:40 PM »

Hello again,

I am planning on moving up in the world of mixing towards bigger and better boards and find myself lacking knowledge about the features some of these larger boards have. I currently mix on a 24ch Behringer (JUNK) and a yamaha LS9. The LS9 has matrices but I'm not sure how and why to use them. We just use Aux's (Mixes on the LS9). Also, explain to me the basics of a VCA (or DCA with the yamahas).

I am going off to college next year and hope to get on board with the sound crew there. I know they use A LOT better stuff than what I am used to and I want to be "in the know" on this stuff when I get there. They use Midas (not sure of any models), M7CL's, and PM5D's for various groups and events.


Thanks again guys.
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Tom Young

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Re: DCA/VCA & Matrix explanation
« Reply #1 on: April 27, 2010, 12:50:13 PM »

There have been at least a few discussions/threads here at ProSoundWeb on VCA's, DCA's and the differences between the two.

Likewise, at least a few manufacturers (of mixing consoles, primarily) provide articles or white papres on these subjects.

I suggest you do some research via these sources first and then come back with specific questions.
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Keith Shannon

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Re: DCA/VCA & Matrix explanation
« Reply #2 on: April 27, 2010, 02:43:22 PM »

Kristian Stevenson wrote on Tue, 27 April 2010 12:41

Hello again,

I am planning on moving up in the world of mixing towards bigger and better boards and find myself lacking knowledge about the features some of these larger boards have. I currently mix on a 24ch Behringer (JUNK) and a yamaha LS9. The LS9 has matrices but I'm not sure how and why to use them. We just use Aux's (Mixes on the LS9). Also, explain to me the basics of a VCA (or DCA with the yamahas).

I am going off to college next year and hope to get on board with the sound crew there. I know they use A LOT better stuff than what I am used to and I want to be "in the know" on this stuff when I get there. They use Midas (not sure of any models), M7CL's, and PM5D's for various groups and events.

Thanks again guys.


A normal subgroup is not much different from the L/R master faders; there is a summing amp that receives all signals sent to the subgroup, a fader that attenuates the signal to the desired level, and assignments to the main outs. You can think of it as very similar to plugging the output of one small mixer into a channel of another mixer; you can adjust the individual levels on the small mixer, or the small mix's place in the whole mix using the channel fader that the small mixer is plugged into.

A VCA group works differently. VCA stands for "voltage-controlled amplifier", and it works kind of backwards; instead of controlling the volume of the summed signals sent to the fader, the fader sets the base voltage that is given to a special gain stage of each channel strip assigned to that group. As a result, the signals on each individual channel are adjusted according to changes in the head amp, their channel fader, AND the VCA group amp stage, before the signals are ever summed onto a bus.

The main advantage of a VCA group is that the actual change in channel gain affects more than just the summed output of the group to the master bus, but all post-fade aux outputs as well (and if desired, the insert). Pre-fade auxes are usually picked off before the VCA gain stage (keeping the basic idea of the pre-fade aux as being dependent only on the head amp and maybe the EQ stage). That allows VCA groups to be actual "submasters", controlling the level of each channel in all outputs that the channel feeds; if there's too much drums in the mix, you can back off the drum group fader, and both the live mix fed off of L/R/M and the recording feed sent from post-fade Aux5/6 will have the drums reduced. With a traditional subgroup, backing off the group fader only adjusts the live level, requiring channel fader or aux send tweaks to reduce it in the recording, which can upset your delicately-balanced drum mix. Matrices were designed to mitigate this shortcoming, by providing a "group-fed aux" that would react to changes in the group faders just like the master outs.


DCA is the digital equivalent of VCA, however because the signal is digital by the critical point, it isn't amplified, but processed in the equivalent way to increase or decrease amplitude. There are a couple of ways to accomplish it in the digital world; the mixer's data processing may emulate a VCA by inserting a gain processing step after the signal is cloned for pre-fade sends, or it may achieve a similar practical result by "ganging" the channel's fader and post-fade mix sends to the DCA fader, adjusting them in proportion to their individual "unity" levels.
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Kristian Stevenson

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Re: DCA/VCA & Matrix explanation
« Reply #3 on: April 27, 2010, 02:55:27 PM »

Thanks for that explanation. I searched around on this forum and couldn't find much of an explanation like what you just gave me.
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Mike Kivett

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Re: DCA/VCA & Matrix explanation
« Reply #4 on: April 27, 2010, 04:32:28 PM »

Here's a link to some white papers on these subjects.

http://www.soundcraft.com/support/white_papers.aspx
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Kristian Stevenson

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Re: DCA/VCA & Matrix explanation
« Reply #5 on: April 28, 2010, 06:41:43 AM »

Thanks. That helps a lot.
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John Fiorello

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Re: DCA/VCA & Matrix explanation
« Reply #6 on: May 14, 2010, 12:38:26 AM »

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ProSoundWeb Community

Re: DCA/VCA & Matrix explanation
« Reply #6 on: May 14, 2010, 12:38:26 AM »


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