okay, this is the second in a series of posts that will cover a variety of church audio fundamentals. this stuff will really only appeal to our beloved tech folks. but it wouldn’t be a bad idea for our ‘talent’ types to peruse this info as well. who knows, might come in handy someday.
so, let’s review some church audio fundamentals …
four basic steps to a church sound check
- make sure it works
- set gain structure
- set monitors
- set house
so for this post we’re gonna be talking about step 2, gain structure. oh joy.
so, what gain structure is and why do we care? let’s take a minute and talk about that, shall we? apologies again to our artsy folks. this is gonna get dull…
audio signal levels exist naturally on a continuum from a super tiny barely detectable level coming out of a microphone, all the way up to the thousands of times more powerful signal coming out of a power amplifier. but, for the sake of simplicity, it’s handy to think of these levels as falling loosely into three categories; mic level, line level, and speaker level.
mic level is the signal generated right out of a microphone, and it’s really puny. line level is generated by things like keyboards, mixers, wireless microphone receivers, and such, and is kinda a nice middlin’-easy-to-deal-with level. speaker level is what comes out of an amplifier and drives a speaker and can be quite powerful. [with the right power amplifier, it is actually possible to 'weld' metal with the outputs. and no, don't ask me how i know this...]. if you want to geek out more on this levels stuff, go here.
so, the purpose of setting our gain structure is to make all these wildly varying signals mesh together. now, from a practical standpoint, what that means is we need to try each input one at a time [and push 'solo' or 'cue' or some such on our mixer so we can see the level on a meter] and twiddle the ‘gain’ [or preamp, or head amp] knob until the level we are getting into our mixer is in the right range.
so, what is the right range? well, conventional wisdom used to be that you wanted to get the level as high as possible without it getting into the red very often, thereby overcoming any inherent noise in the mixer. if you occasionally hit the red, that wasn’t so bad as long as it wasn’t glowing like a stoplight. well, in my opinion, things have changed. you see, electronics have improved by leaps and bounds in the past couple of decades, and you can now get equipment with very low noise specs very cheaply. also, we are now firmly into the digital age, and that means we are often setting levels for digital equipment as well. when analog equipment goes into the red, it begins to distort, but often [depending on the gear] it does so only minimally. so there is room for error there. digital gear doesn’t act like that. when you ‘hit the wall’ with digital equipment, it’s ugly. put simply, there is no headroom in digital.
so, speaking very generally, the right range is probably somewhere in the middle of the meter’s travel. this gives lots of headroom without sacrificing anything substantial with regards to noise, etc. it also means that when your singer suddenly gives a ‘holy shout’ it’s not gonna peg your mixer into the red.
finally, it is very important to set this level before you attempt to set anything else. everything else in the signal chain comes after this point, so you need to get this one right. if you have to go back during the show and lower the gain knob, it’s gonna affect all the other levels you set, like monitors, or effects sends, not to mention your overall mix.
okay, i’ve glossed over tons of stuff in this, so feel free to drop me a line if you have a specific question. or you can also drop me a line to say hi. i like it when folks say hi.
and stay tuned for our next installment, setting monitors, where we get to interact with actual musicians. ewwwww…
bfn,
brian
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