Beginners Look at a Live Mixer: Gain

In the last post, we looked at the inputs of a Soundcraft EFX 8 mixer. Today we are going to look at the very next stage, the channel gains. This is a confusing topic because a mixer controls volume at many stages, so it would seem odd to some. At the end of this post however, I hope to have explained it well enough that it makes a bit more sense.




The Soundcraft EFX 8, what I will use
as an example in this series.

To explain the gains, we need to consider signal to noise ratio. When a signal goes through electronics it will pick up noise. The noise is often hidden, especially if it is good equipment and a loud signal. 

This is the first and main point of having gain. It is a way to maximise the volume before it goes through any noise adding electronics so the noise is less audible. This is known as having a good signal to noise ratio.

If the gain was set really low, and it was a noisy channel, you would have to turn the volume up later. If the noise has already been introduced, then turning up the volume will only increase the noise volume as well.

To know how high you can turn the gain, use the VU meter. Hit the channel's PFL (pre fader level) button and turn up the gain until the loudest bits touch the red light. Turn it down a touch so it stops hitting the red and you are set. Do this for each channel.

There is also a peak LED under PFL and Mute 
that will light if the track is clipping, turn the gain down just 
until it stops lighting up.

While the gains are for what is described above, I often use them for another reason as well. In my experience, noise isn't a huge issue unless you are recording. If you are doing a small event especially, the sound setup after the mixer may not be great and mean noise gets played anyway.

So once I have set up the gains for optimum signal to noise, I often will tweak them. The reason for this is to ease control of the faders when actually mixing. I will explore the faders in detail in a later post however, I will say each fader controls the volume of the instrument in the mix.

For a good level of control, you want to be able to turn each channel up and down in the mix. That's why I like to have all the faders starting around 0dB, there is room to turn it both up and down, quite a lot. This is good for if a singer sings quieter in one section and you need to boost them while turning down the guitar as it's too loud.

With gains set right, you have plenty of room to move the faders
both above and below 0dB.

So, with this fader configuration starting at 0dB, I will want to adjust the gains so that the instruments are all roughly the same volume. That way the faders are able to fine tune from that point. Since you have already set a good signal to noise ratio, you will probably find you don't want to turn any gain up more, otherwise it will clip. So if something is too quiet, turn the other gains down a bit.

In the end, do what you like, everyone has their way and hates other people's methods. Just don't let it go into the RED!