I second the suggestion of using TheatreMix, but I think you are a way from adding that to your setup.
The first thing you need is a better understanding of gain structure in order to get the SQ doing what you want it to do.
If your desire is to have all of the channel faders at unity as your base, setting all of the input gains to -18 is not going to get you there. As you’ve already discovered, every input source is going to reach the desk at a different level, and the gain control is the first* step in bringing everything together. You need to adjust gain for each channel to bring the signal up (or down) to the level you want. Normally, this would be a few decibels below 0 on the meter most of the time, and a few dB above it on the loudest peaks. In general, microphone signals will be low, and need to be raised quite a bit. Instruments coming in through a DI, including direct XLR outs from an amplifier, will be significantly hotter and some, especially keyboards, may need to have the input gain lowered. This will get you to a decent baseline, but you still have to actively mix the show. It will also give you a good starting point for anything you send to an AUX.
- Sometimes the first step is to have the musician reduce their signal level to you in order to give you control over the mix.
Once you have the incoming gains set, and your output masters at unity, you need to set the amplifier gains so the loudspeakers produce the level of sound you need in the room, and at any AUX destinations.
A few words about auxiliary (AUX) mixes. Ignore what you have read. Yes, they are used for “monitors”, especially in live music, but that is not their only use. An AUX is a signal created from the input sources that is sent somewhere other than the main speakers. An AUX can contain all of the sources, or only some of them. They can be set up as PRE-fade, where the signal is created before the channel output fader so changes to the LR mix don’t affect the AUX, or POST-fade, where raising or lowering a channel in the mains will also do it in the AUX mix. In theater AUXes are typically used to create program feeds to go to different offstage areas, assisted listening systems, recording, etc, as well as monitors for pit musicians. All of these will be POST-fade except the monitors, and even those aren’t always PRE-fade. Whether they are PRE or POST, the level of each channel going to an AUX can be set individually.
Groups (GRP) are used to control multiple channels with a single fader. When you assign a channel to a group you normally remove it from the main LR mix, and send the GRP there. All of the assigned channels will have their level raised or lowered the same amount whenever you adjust the GRP fader. GRPs have processing, and insert busses, making them very useful for applying the same EQ/Compression/Gate/etc. to a bunch of channels. When doing corporate audio on small analog mixers, my practice was to assign all of the lav mics to a group and then run that through an inserted EQ – not as good as a full parametric on each channel but better than nothing.
This gives you your basic setup with all of your faders beginning at unity. No matter how well you get this dialed in, you will still have to change the mix during the show because someone will be playing or singing louder or quieter then normal. Or a mic gets moved in the pit and no one puts it back.
You may also have to adjust the level of an entire mix, and the easiest way to do that is with its master fader, since most of the time the amps aren’t going to be accessible.
