A DCA is the digital equivalent of a VCA (Voltage Controlled Amplifier).

While a VCA uses an analog electrical current to control volume, a DCA uses numerical data and digital processing to perform the same function.

It's a very common term in digital mixing consoles (such as the Behringer X32 or Midas M32). In these consoles, a "DCA Fader" acts as a remote control that changes the volume of a group of channels simultaneously, without physically passing the audio through it, but rather sending gain instructions to the individual channels.

It is also found in digital synthesizers as the final stage that sets the sound volume (usually controlled by an envelope).