Proper gain staging (or gain structure) is a critical skill for any audio engineer to develop, and arguably the single most important determining factor in the overall quality of a mix. Proper gain staging can lead to a mix that is clear, free of extraneous noise, appropriately loud, and with plenty of headroom. When gain staging is not done properly, the result can be a mix that is full of noticeable noises and hiss, not loud enough, or, perhaps worst of all, characterized by unpleasant distortion or clipping.
Gain management is of heightened importance in the era of digital audio. In the days of all-analog signal flows, overloading an individual gain stage would often be seen as a beneficial effect, imparting “warmth,” “punch,” or “fullness” on a signal. Unfortunately, the effects of digital distortion are far less pleasant on the ear, and care should be taken to avoid clipping in a digital signal chain.
A gain stage is any point in a signal chain at which the level of the signal can be altered. In this article, we’ll discuss gain staging from the perspective of using a digital console for live sound mixing, but many of the principles here are equally applicable to mixing in a DAW, or on an analog console.
#1: A Clean Signal At The Source Is Key
We’ve all heard some variation of the phrase “garbage in, garbage out” in reference to properly capturing audio at the source. This is especially important advice when it comes to gain staging. For example, if a lavalier or headset mic is improperly positioned to pick up a speaker’s voice, it may be necessary to crank up the gain on that channel, unnecessarily raising the noise floor. A vintage electric bass guitar’s pickups might have a weak output, necessitating the use of an active DI to bring the signal to an appropriate level for your mixer’s input. Similarly, some dynamic mics are known for their low output levels, and can sometimes benefit from the use of an additional phantom-powered ‘clean’ preamp. You’ll notice that the last two examples involve the addition of extra gain stages, which brings us to our next tip…
#2: Your Mixer’s Preamp Is Not The Only Gain Stage
At first glance, you might think there’s only one gain stage to worry about in the signal flow of any one channel: the knob labeled ‘GAIN,’ right? Of course, there’s a lot more to it than that. Thinking back to our previous tip, there are often multiple gain stages to consider in a signal chain before it even reaches the input of your mixer. In addition to the examples given above, wireless mic receivers usually have gain control, and it’s important to set the gain properly to deliver a strong signal to the mixer without distortion.
Gain structuring considerations don’t stop once a signal passes through your mixer’s head amp. While we don’t think of it as such, the channel EQ is a gain stage that deserves consideration. Whether you’re making additive EQ changes (i.e. boosting the gain of certain frequencies) or subtractive changes (i.e. cutting the gain of certain frequencies), you’re impacting the overall gain of the channel. Dynamics processors (compressors, gates, expanders, etc.) by their very definition have a huge impact on gain, and in fact most have a ‘makeup gain’ control – that is, yet another gain stage to take into account.
Finally, we come to plugins. While the use of hardware inserts in live sound applications becomes rarer by the day, the use of software plugins has exploded in recent years. Many digital console manufacturers have gotten into the plugin game themselves, offering plugin bundles for purchase alongside their hardware, or bundling them in for free with their consoles. The digital nature of plugins means they are often overlooked as a gain stage, but they have the same impacts on your signal as the analog hardware they are often designed to emulate. It’s important to take into account all of the gain stages a signal will pass through, to maximize headroom and minimize noise and distortion.
#3: Think About Optimal Fader Placement
To the untrained eye, a fader on a console looks like a tool that makes linear adjustments. In other words, no matter where the fader is positioned, moving it by one centimeter should have an equal impact on the signal level. Of course, we know that’s not the case; faders operate logarithmically. To put it into the simplest terms possible, faders are more sensitive to adjustments the closer they are to their ‘0’ or ‘Unity’ point. Thus, in order to have the most precise control over your mix, you should aim to structure your gain so that you end up mixing with all your channel faders near unity. Some engineers will even set all their faders at unity during sound check, and adjust levels with their gain controls to ensure maximum control when it comes to showtime. This practice isn’t strictly necessary, or even recommended by most, but it goes to show that optimal fader placement is worth taking into account.
#4: Leave More Headroom Than You Think You Need
‘Headroom’ is the difference in dB between the normal operating level of your channel or mix, and the point at which the signal clips. It’s tempting to decrease your available headroom and squeeze the maximum signal level possible out of your mix, but keep in mind that sudden, unexpected signal peaks are a fact of life in live sound mixing, for a variety of reasons. It’s better to have a slightly quieter signal overall, in exchange for avoiding the ugly sounds of digital distortion.
There’s more to think about in gain staging than first meets the eye, but by following a few simple principles, you can make the most of your gear by achieving optimum levels and maximum headroom with minimal distortion and noise.
TC Furlong Inc.’s engineers have the experience to make your next live event sound great. If you need top notch gear and technicians for your next event, get in touch with one of our Project Managers at 847-367-9588.
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