hello and welcome back to the channel. today i wanted to talk about two huge
myths regarding the console gain control for live
sound. the first one, the gain control causes
or fixes feedback. this is one of those things where there's a grain of truth
and a whole lot of misunderstanding in that statement. feedback doesn't care
where the level comes from. i talk a lot about the importance of
signal flow and this is another case where
understanding signal flow helps to understand where this myth
that the gain control causes or cures feedback comes from.
if you follow the singer's microphone into the console, it comes to the gain
control at the preamp stage. everything else in the channel is after
that gain control. everything in the channel is impacted by
that gain control. here we see four monitor feeds, an
effects send, and our front of house feed.
if monitor mix 1 is 3 db above the threshold of feedback,
then if we turn the gain down 3 db or more,
then of course the feedback will stop.. but we also turn down
everything 3db by adjusting the gain, since the gain impacts
everything after it. not just monitor mix 1,
which in our example, was the only place that actually needed to be reduced
3db. by the same token, if the house was 3 db
under the threshold of feedback on that channel, and you turn the gain up 3db,
then of course you'll get feedback in the house pa...
and you also turned everything up 3db in that channel!
changing all of your channel's sends in the process.
the gain needs to be set where the input meters tell you
the gain needs to be set. there is no connection between running the gains
high and the level of the gain control itself
causing feedback, except in correlation with the other
settings. i'm sure at some point someone has
gotten feedback and turned down the gain, the feedback went away, and they thought
they'd found the magic gain setting where it was the cause of the feedback.
but in reality, they turned down everything on that channel strip
and of course feedback went away in the process... and it also changed the monitor
mixes on that channel. so that's number one. let's talk about
number two- reducing the gain control reduces
background noise picked up by the mic. this is another
misconception. think about the signal-to-noise ratio.
the signal-to-noise ratio is basically fixed for the mic.
if you reduce the gain 6 db on an open mic, the background noise that is being
picked up by the mic will be reduced 6 db.
that much is true. and then when the singer steps up to the mic to sing,
their voice, the signal, will also be reduced 6 db
in the mix. once again we're back to signal flow.
the gain control doesn't exist on an island.
in the case of our example, as soon as we bring our channel fader back
up to compensate for losing 6 db off the singer's signal,
their voice, then that background noise will also be increased by 6 db.
we just went effectively in a circle. not only that, but by adjusting the gain
control when we didn't need to, for the wrong reasons, we changed all of
the send levels and wrecked any mixes we'd already set up.
at least on that channel. the gain control really only has
one purpose: to optimize input levels of the channel.
that means to adjust it for consistent levels compared to other channels,
with headroom, away from clipping. it's not to be used for a volume control.
the input meter or pfl meter will show you the information that you need so
that you can consistently set your gain. this information is for any console.
analog or digital. i'll leave a couple of links here for
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