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F.O.H. 101 // Gain Staging

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The most important thing that we as audio engineers do is get signal from instrument to speakers.  But to do that, the signal (at its most basic level) must first pass from the instrument into a microphone or DI box, down a line, through a snake, into a console, into a preamp, through an equalizer, through a power amplifier, down more line to a crossover and then finally to the speakers and into our ears.  More advanced systems add AD converts, compressors, gates, a second equalizer, aux sends/returns, effects sends/returns, matrices, DA converters, and a whole plethora more if being shunted into an Aviom system.  The neat part of that absurd chain is that, at nearly every level, we have the opportunity to manipulate the signal to our whim – and that it all happens at very near the speed of light (literally).  The drawback is that, overtime, the signal degrades and your signal-to-noise ratio (how much equipment/Earth noise will be ingrained into the audio signal) will increase.

What Is “Gain?”

Gain is an inherent ability in amplifiers of all sorts which increases the amplitude, or power, of an electrical signal.  In essence, they make a weak signal more powerful, a quiet noise becomes louder.  They also work in the reverse, weakening strong signals to make loud noises quieter.  Preamplifiers “gain up” a microphone signal from mic-level (0.001 volts) to line-level (~1.2 volts), where power amplifiers take that line-level signal and bump it up to speaker-level (between 1 and 50 volts, depending on the speaker).  On top of those two basic levels, almost all digital effects and analog outboard gear also have built-in amplifiers.  The reason for this is to allow the user to properly set the signal strength at each level of the chain, so a strong audio signal with as little background noise as possible is relayed through the speakers and to our ears.  This individual control at each level in your signal flow is called gain staging.

Gain Staging

I cannot stress enough how important proper gain staging is for an audio engineer.  A weak signal coming into your system will be a weak signal heading to your effects, a weaker signal returning to your console and an even weaker signal sent to the speakers.  The paramount step in the entire system is input gain from the sound source.  The input gain coming into your system direct from the sound source controls how much signal is sent through your aux sends to your effects, your monitors, your speakers, everything.  A strong input gain relays a strong signal throughout your entire chain, masks background noise (such as 60-cycle hum, fuzz and hiss caused by electrical components), and provides the best signal possible for effects and monitors.

Gain Stage Order

PREAMP:  Always start gain staging with the preamp.  You want to make sure your signal is strong, but not clipping or causing feedback.  Adjust the gain dial on your preamp to just below the 0dB (clipping) marker on the input meter.  Everything else in the chain relies upon this.  From here, the signal will be sent to the channel fader and the…

FILTERS/EQUALIZER:  From there, set your filters and your equalizer appropriately, because the end result of that stage will be send to the channel fader and power the…

DYNAMIC PROCESSORS:  such as compressors and gates.  Use the makeup gain setting on your compressor, and the threshold on the gate to determine how much signal will be returning from these dynamic processors and be sent back to the channel fader and to the…

TIME-BASED PROCESSORS: such as reverbs and delays.  Quality reverb and the strength of the delay rely upon how much signal is being sent to them.  The output of the time-based processors will be sent to designated effects return and channel faders, as well as the…

MONITORS: When using aux sends (sent pre-fader, of course) to create monitor mixes, the signal we have compiled so far will be routed back to the musicians for use as their monitor mix.  Depending on your setup, one or more individual channels will be routed to each musician on stage, either in a group or individually.  However, what they’re hearing is a closed loop, and does not effect the…

CHANNEL FADERS: which are a crucial part of gain staging.  Because the higher the decibel marker the fader is at, the higher the gain of that channel, and once we get our fader levels up to just below the 0dB (clipping) marker on the output meter, we can adjust the…

GROUP FADERS: if you have any.  These are also called sub-mixes, or sub-busses.  And once we get our fader levels up to just below the 0dB (clipping) marker on the output meter, you will notice that everything is now being sent to the…

MASTER FADER(S): at an appropriate level.  Your effects return, channel and/or group faders may need to be adjusted so that their combined outputs aren’t causing your overall level to clip by exceeding the 0dB marker on the output meter, while the master fader is at nominal level (odB on the master fader).  The master fader will then send the entire chain to the…

POWER AMPLIFIERS: which bump up that line-level signal to speaker level, and then send the signal to the…

SPEAKERS: which can usually be set at a certain decibel level on the unit themselves.

Engineers running an Aviom systems, or multi-track recorders will have additional gain staging steps, but it’s nothing too drastic or complicated.  Individual Aviom users can adjust the gain from each of the inputs into the Aviom unit, and the input gain on multi-track recorders may need to be increased on the recorder itself if the signal coming from the system is at a low level.  Engineers using various matrices will need to set the output gain of the matrix (via fader) to be sent to the matrix speakers.

Improper Gain Staging

It’s easy to see here, that a weak signal at any of these stages will have an adverse effect on the rest of the chain.  As audio engineers, we have to balance input and output gain effectively in order to achieve the best sound possible.  It does not matter how how masterful your EQ work is, how perfect your compression and gating is, or how perfectly synced your delays are – if you have a weak input signal from the sound source, your mix is going to sound bad.  You’ll be forced to use a noisy signal, and push it harder on the faders in an attempt to fit it within the mix, but even this is difficult.  Your mix will be off, and the overall production will suffer.  It’s important to remember that EVERYTHING on a line receives the effects of what you’re wanting to accomplish with the sound.  Compression and low-frequency boosts in the equalizer will make the noise louder, it will be added to the reverb and the delay along with the rest of the signal you’re working with.  Maintaining a stronger signal by proper gain staging will mask that unwanted noise, increasing your signal-to-noise ratio, and providing a higher-quality sound.

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One Response to “F.O.H. 101 // Gain Staging”

  1. Great stuff, Fox. Understanding that “signal chain” is so key–I hope this article helps a lot of newbie volunteer sound guys to improve their gain staging.

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