#8 Improper gain staging
So much is misunderstood about gain staging in the audio world, especially in the church sound.
Years ago Mackie gave instructions in their analog owners manuals about setting ‘unity-gain' "Select solo on the channel you are working with, set the fader at ‘unity,' turn gain knob up until you have the level on meter averaging ‘0'. "
If you set the gain too low you will introduce noise into the channel strip. In a digital mixer, you will be digitizing this noise. If you set the gain too high and the pre-amp overloads, you will be distorting the pre-amp, and from that point on in the signal chain, you will have a distorted signal.
Here are a couple of "fail" scenarios I have run across in regards to gain.
Improper gain staging at the mic-pre-amp
I was hired by a consultant to mix at his church, and after I set gain structure in my console on all inputs, we had a sound check. I started building my mix. The consultant wanted to see all my faders at "unity gain" and constantly adjust the gain levels so my faders would always be at "0."
Not correct gain staging. When I see a Sound person with all faders at "0" it usually a dead give away they do not understand proper gain structure. Setting the gain level gets the best Signal to noise ratio for that channel input. The fader position is for the appropriate setting in relation to the mix.
Improper gain staging in a mix.
I had a complaint about an Aviom system from a vocalist. The singer could not hear or herself. So the Aviom must not be working correctly.
The Monitor system was working because I checked it before the singers arrived. So I go on stage, put in a set of ear-buds and listened to her mix.
Her IEM pack was at about 10' clock, the master out on the Aviom mixer was at about 10' clock, her vocal mic was maxed out as well as nearly all band channels.
I turned the Aviom Main out up to 3' clock, turn her IEM pack up to 3'clock, turned all inputs on the Aviom mixer off. I then turned her mic up to about 2' clock (I wanted to make sure she had a little headroom left.) I turn all the other vocal mics up until they were just under her mic level. I panned the vocals in relation to where they were standing on stage to her. I turned up the piano on her mixer so she could have a pitch reference. She thought I had invented the wheel. All I did was adjust the gain stage of her mixer and IEM pack and rebuild the mix.
Improper sensitivity setting on wireless mics
A lead vocalist is distorting in the video mix. The video director wants to cut the aux worship leaders aux send feeding the recorder -3 dB. FOH person cuts the mic-pre by -3 dB. Distortion is still there.
Looking at the wireless mic receiver, the audio meter is in constant red. Gain on the mic transmitter (called sensitivity on some brands) was reduced 6 dB on the handheld, increased by 6 dB on the pre-amp and distortion was gone.
These are simple common sense solutions that don't involve any math.
Make sure your gain adjustments are made during sound check. If you have to go back and adjust gain levels make sure you warn everyone on monitors because it will affect them.