JAY X said:
Hi All!
Latelly i have heard this thre letters quite often: DCA. Ok, it stands for Digitally controlled amplifier, but it does not seem to refer to a particular device or model of chip.
In the world of live sound mixing consoles, "DCA" is misused in the same way as "VCA." By this I mean: the faders on a console labeled "VCA" or "DCA" should be called "VCA group master" or "DCA group master."
Why?
In an analog console with VCAs, the channel fader does not pass audio. Instead, it sets, based on channel fader position, a control voltage for the voltage-controlled amplifier through which the channel audio passes. It is the control voltage which determines channel level.
Now all VCA consoles have the concept of VCA grouping. A VCA group fader controls the level of all channels assigned to that group. Each VCA group fader outputs a control voltage relative to fader position. In each channel, the channel fader control voltage is added to the group control voltage to determine the actual VCA gain setting. The ultimate effect is that moving a group fader is exactly like moving the channel fader. (This is different from audio subgrouping, where the channels feeding the group are summed and then the group fader affects the final level of that group. From a mix perspective, the real difference is that a VCA group fader move affects post-channel-fader aux senses whereas a subgroup fader move does not.)
The "DCA" concept is analogous (sorry for the pun). It should be obvious that on a digital console the channel fader, like on the VCA console, does not directly manipulate the channel's audio level. Instead it outputs a position-dependent number which represents intended gain. The DCA group fader does the same thing, generating a position-dependent gain-set number. For each channel, the processing determines actual gain by considering the channel position number as well as the position number of all assigned groups, and comes up with a final scale factor.
So, calling the faders "DCAs" is correct in the sense that they are "digital controls" and the "amplifier" is a multiplier in some processing pipeline. But they should still be called "DCA Group" faders.
sorry for the length. coffee good.