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Author Topic: Church Sound: 2.5 Ways To Set Up Input Gain  (Read 796 times)

M. Erik Matlock

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Church Sound: 2.5 Ways To Set Up Input Gain
« on: October 22, 2018, 02:40:31 pm »

Church Sound: 2.5 Ways To Set Up Input Gain
Comparing the “Faders at Unity” and “Maximized Preamp Gain” schools of thought, along with a third hybrid approach...
By Mike Sessler • October 22, 2018

When it comes to live sound, input gain is one of those things you have to get right. If your gain structure is wrong, no amount of EQ, compression or fancy plugins will fix it.

Over the years, I’ve seen my share of gain disasters, and have found many who simply don’t know how to properly gain stage their console.

I’m going to offer you two ways to set up your gain, plus a hybrid approach (the .5). There a few schools of thought on how to set gain, and it’s hard to say that one is “right;” it really depends on many factors. There are some wrong ways to do it, however, and we’ll get to those in a moment. First, let’s define input gain.

Input gain is the gain applied by the console to mic and line level inputs coming into the each channel. Most consoles have a gain knob at the top of the channel strip labeled “Gain,” “Input Level,” or sometimes confusingly, “Trim.”

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Ken Webster

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Re: Church Sound: 2.5 Ways To Set Up Input Gain
« Reply #1 on: October 22, 2018, 07:19:10 pm »

Hi, I am not sure what setting the faders at unity means.  Our faders are marked from zero to – infinity.  I assume unity means output = input so this would mean setting all faders at their maximum (zero).  Which would mean the faders can only be reduced from there.  This would mean that if I want to boost 1 input only. I would have to attenuate every other fader and boost the main output to compensate the attenuation which seems rather cumbersome.  We use a mix of balanced and unbalanced sources and the unbalanced sources are RCA inputs which are not subject to the gain control as this is a well-defined signal level standard.

What I do using a Yamaha MR analogue console and you can comment if you like, is:
Initially set all input channel faders at mid-scale (-15)
Set the softest vocalists input gain to a notch below clipping or if it doesn’t clip (usual case) pretty near maximum (SM58 mics).  Then set the other vocalists to mix with this.  So, I am using the input gain to get an initial vocal mix because the monitoring system is not subject to fader setting.  Doing it this way allows me to use the monitor cues and headphones to exclude all but the channels I want to hear which makes it easy to get the levels close fast and then fine tune blend vocalists.  We used to have a band years ago but resorted to using CDs when all that fell apart.  We do have some musicians again but only a small team who are rostered on once a month or so.  The rest of the time we are running worship music from a PC.  The PC is connected by RCA, not ideal I know.  I can and do use the PC volume as a gain control to set the initial of default mix.   However, once we have been through practice and the default mix is pretty much there, I do further mixing on the faders.  I think this give us close to maximum input level and maximum group levels so S/N is very good but it also allows flexible and efficient mixing using faders.
The SM 58 mics are not particularly sensitive and the singers being mostly untrained will generally not overload the input stage.  I am generally running close to maximum gain except for one particularly strong voice.

Now we have passive speakers running off a FB (unbalanced) and a FOH (balanced) amp, 2ch 180 W and 2ch 280 W into 8 ohms respectively.  The FB amp has no input gain control, the FOH amp has input gain control.  I have set the FOH gain to match the FB equal output for equal input approx. ½ gain, so the 2 amps have equal sensitivity despite power differences.  These are run from separate channels of a 32 band EQ.  I have set the EQ output so that 0 VU on the console gives 100 dBC at 1 meter on FOH and 95 dBC at 1 meter on the FB.  Max capacity of hall is about 200 people jam packed.  We generally don’t have more than about 70 in a service so not running at anything like maximum output.

This level of foldback is an experiment, we used to run it lower but it wasn’t terribly useful and we had no way for the sound guy to tell what it may be like on stage.  This way, the console meters give us a guide, if the FB and FOH meters are the same, the FB though softer will be at a useful level. I tend to only have vocal in FB if the music is loud but add a little music if soft seems help vocalists with pitch and timing.

It's a difficult stage area in a brick corner without acoustic treatment.  We do have to be more careful with feedback at this setting, it does impose a severe ceiling on FB levels.  There are limits to ringing out after all.  I know we are kind of unusual in lacking musicians and using music files but maybe someone can benifit or recommend a better way, it just reflects our journey so far.

« Last Edit: October 22, 2018, 08:54:58 pm by Ken Webster »

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Re: Church Sound: 2.5 Ways To Set Up Input Gain
« Reply #1 on: October 22, 2018, 07:19:10 pm »

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