Master Output Section
The output section has faders for the 8 group outputs (which are bus masters) and the Left/Right L/R Mix on the right (or STEREO on some boards). Any of the buses can be soloed.
The Mackie 8-bus board has the ability to use the 8 group outputs as subgroups for the Left/Right mix. This is referred to as a submix. For example, if you were designing a stereo mix but wanted a group fader to control all your synths and another group fader to control all your mics, you would follow this procedure:
1) Unassign your mic and synth channels from the L/R Mix.
2) Select a group you would like to use as a subgroup for the synths and assign the synth channel strips to that group: do the same for the mics (for example, assign the mics channels to group 1-2 and the synths to group 3-4).
3) Pan each channel strip where you would like to image the instrument or mic in the subgroup (unless using MONO).
4) Above the subgroup fader, choose L MIX, R MIX, or L+R MIX, depending on where you want your subgroup imaged. Normally, to keep the stereo image, you would have the odd-numbered groups assigned to L MIX and the even-numbered groups assigned to R MIX.
5) If you really want a mono subgroup, be certain to depress both L and R MIX in addition to pressing the MONO button above
6) These faders will now act as subfaders to the Left/Right MIX fader, so you can fade out entire groups with a single fader, rather than grabbing all the individual channels faders.
On digital boards, for sub-mixes it is possible to gang subgroup faders so if you move one, the group moves physically along with it. On boards such as the Midas M32, individual input channels can be assigned to what are called DCAs or Digitally Controller Amplifiers, similar to the Mackie 1-8 buses. These work like the 1-8 group faders above when in subgroup mode, except that they will adjust the level of each input channel individually, as opposed to summing all the channels into one signal channel and then adjusting the level of that channel. So it is possible to have those input channels going to different output locations if you wanted, but their various levels would be controlled by a single DCA, which has many cool possibilities.