Using the following optional modules enables the unit to perform their functions: Two D-983s for providing a maximum of 48 contact inputs and 32 contact outputs, D-984VC for VCA control. Its audio input/output and control ports can accept optional plug-in modules, making the unit have a maximum of 32 inputs or 32 outputs and up to 2 control modules.

A built-in powerful signal processing function permits the unit to be used as both a mixer and a signal processor. The Q-2008SPD Digital Mixing Processor Unit is designed to have up to 32 audio inputs and outputs in total, and to be mounted in an EIA standard equipment rack (3U size). (*1) Automatic Resonance Control function automatically creates the filter curve to improve sound clarity by measuring the acoustic characteristics inherent in architectural space. It can be mounted in an EIA component rack (4U size). However, it can also be operated by connecting the PC or optional Remote control panel. Furnished with various function setting buttons and 14 analog volume faders, the M-864D can be operated without need for use of a PC. Advanced acoustic compensation can be automatically performed without using an acoustic measuring instrument.

It is equipped with digital signal processing functions such as Automatic resonance control function (ARC(*1)), Feedback suppressor function (FBS), Automatic stereo input mute function (AUTO MUTE or Ducker), and Equalizer. The M-864D is a 4U rack mountable Digital stereo mixer having 22 input channels including 8 monaural input channels and 7 stereo input channels, 6 output channels including 4 monaural output channels and 1 stereo recording output channel, and 4 bus channels.

Mixer for 2 pc