What is gain in audio?

Within the discipline of audio production, there are numerous terms that can be confusing, especially for beginners. One of them is "gain." You might have come across the word “gain” while working with audio equipment or reading blogs like these. But what exactly is gain, and how does it differ from volume, level, trim, signal strength, and other such terms? 

In this article, we'll delve into the concept of gain, unravel its significance, and shed light on its distinctions from other similar terms. Whether you're an aspiring producer, musician, or audio enthusiast, having a clear understanding of gain will empower you to master sound control and achieve optimal audio quality. So let’s embark on this sonic journey and unlock the mysteries of gain.

Follow along with the Lindell Audio 50 Series console from Plugin Alliance, a powerful console with an array of choices for creating professional-sounding drums, guitars, synths and more with attitude and presence. 

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What is gain?

At its core, “gain” in audio speaks to the difference of input level between the input and output of an amplification circuit. This is why gain staging—the act of routing devices in series without adding noise-floor issues or unwanted distortion—is so important to us audio engineers. 

But in order to truly understand this definition, gain has both a technical definition and some unfortunate, idiomatic uses that we need to think about. 

An appeal to the authorities tells us that gain is the strength of an audio signal within an amplification circuit—or put more finely, gain is the difference between the level at the input stage of an amplifier and an output stage.

Idiomatically, gain has come to take on many disparate meanings. Many use it interchangeably with “level” or “signal strength”—terms we’ll define later. Among guitarists, gain has become a way to describe the amount of distortion you’re introducing into an otherwise clean electric guitar tone. Such vacillations and imprecisions in language may be inevitable, but they’re still confusing. 

Volume, level, loudness, and trim—oh my! 

As we have done for gain, let’s now try to define other concepts so you can keep them straight in your head—and out of gain’s way.

Level refers to the overall amplitude or intensity of an audio signal. Left unqualified, it functions as the umbrella for many of the others listed in this article. When coupled with something like “voltage” or “sound pressure,” level becomes an expression of a signal’s intensity in that particular scientific classification.

Trim, a term commonly used in mixing consoles and digital audio workstations (DAWs), refers to the fine adjustment of the signal level. A trim pot or knob allows you to make exceedingly small changes to the signal strength level of an audio source. 

Loudness, in pro-audio circles, refers to matters of listener perception—whether an audio track appears to have more density and strength than another. It’s somewhat subjective and tied as much to arrangement and frequency balance as it is to the signal level of playback. A gunshot, for example, will always feel louder than a bassoon, even when played back at the same level. This has to do without the sound’s innate weight, density, and frequency balance, all of which contribute to the concept of “loudness.”

Volume is a purely an idiomatic expression of level. It shouldn't have a place in the jargon of engineering, as “volume” literally refers to the amount of space something can take up in the physical world. Still, time has beat us all into submission, and we all use the word in matters of sound. 

As many devices have a “volume controller” or “volume knob,” volume has come to define the level at which an audio signal is played back through the final listening system. As such, a volume knob does not alter the actual signal itself within any recording or mixing device, but adjusts the level at which it is delivered to the listener. 

Volume is often expressed in terms of subjective units, such as "loud" or "soft," rather than specific dB values. When it comes to gain vs. volume on something like a guitar amplifier, gain is the input level within the amps, and volume is the output level that goes to the speaker. 

Gain versus distortion 

Although gain has come to describe overdriven distortion among guitar players, the terms “gain” and “distortion” are inherently different.

Gain is a function of a sound’s signal level within the circuit of an amplifier—the difference between the input level and output level, as we’ve stated before. 

Distortion, on the other hand, occurs when the audio signal is altered in a way that deviates from its original waveform. Distortion is characterized by the addition of harmonics and artifacts into the original signal, resulting in a more aggressive or gritty sound. 

Distortion happens when the gain is stronger than the circuit was designed to handle without introducing these harmonics or artifacts. It’s the sound of the amplifier reacting to how hard it’s being driven. 

That gain knob on a guitar amp was originally intended to set the level within the amp.  We guitar players just happened to like it when it was cranked too far. We’re also as a rule not very word-conscious, so we came to call distortion “gain.

Does gain affect sound quality?

In hardware, the answer is usually yes. In software, it depends. 

Some digital gain controls are clean. They won’t add harmonic coloration when you introduce level changes. The sound will have the exact same harmonic balance; it will just be louder or softer (or more accurately, stronger or weaker in level). 

Analog circuits are quite different. With hardware, the gain changes often come with innate coloration, because the circuits that facilitate change level changes rely on components that color the sound—things like transformers and op-amps, for example. 

What does this mean for you, the digital producer/mixing engineer? With emulated hardware, such as the channel strips fashioned by Brainworx and Plugin Alliance, you need to consider where you apply gain to a signal.

Types of gain controls

To better understand the kinds of controls that affect gain, let’s examine an excellent emulation of a classic analog channel strip:

This is the Lindell 50, a model of an iconic American channel strip used for both recording and mixing. I’m selecting it because this strip has several different points where gain is affected.

Preamp gain

You’ll note, all the way over to the left, a knob titled “gain.” This control is found in the plugin’s preamp section, and is what we call “preamp gain.”

Preamp gain is typically found on audio interfaces, mixers, preamplifiers, and analog emulation plugins like this one. The parameter controls the initial amplification of the incoming signal from a microphone or other audio source. Adjusting the preamp gain allows you to set the appropriate level for recording or processing audio before it reaches its next step in the chain. 

In this plugin, that means the gain will feed the EQ and compressor sections, running first into one and then the other. 

Makeup gain

Look past the EQ section and you’ll find an FET compressor—which has its own controls that affect gain:

These are dedicated controls to adjust the gain of the signal within the compressor’s amplification circuit. As this plugin models an FET compressor, these gain controls introduce harmonic coloration. They are hardly clean.

The output gain control of a compressor is commonly referred to as “makeup gain,” and it can be found on many classic hardware units. Makeup gain often has its own innate coloration, depending on the circuit: Many love the API 2500 or Manley’s Variable Mu as much for their colored gain as for their compression.

Channel gain

At the end of the plugin you’ll find a fader:

This is as close to a straight, colorless gain control as the plugin provides. In the context of this plugin this is the channel gain.

Channel gain is found on mixing consoles and digital audio workstations (DAWs), usually at the end of individual audio channels. They are commonly represented by faders or potentiometers. These controls allow you to adjust the level of a specific audio channel in the mix with as little harmonic coloration as possible. By adjusting this channel gain on a given instrument, you can balance it in the context of your mix.

Master gain

Another type of gain to consider is the master gain, which is basically the final output control of your whole mix. It’s the fader of your stereo bus in Pro Tools, Logic Pro, Reaper, or other DAW of choice. The master gain is designed to affect the overall level of all the tracks at once in relation to each other. Adjusting the master gain allows you to control the overall level of the mix, and ensure that it doesn’t incur distortion once it hits an analog playback device.

Examples of gain affecting sound quality

Let's take two guitars and listen to them dry, followed by listening to them after cranking the preamp gain on them (level-matched). The compressor has been switched off, as you can see.

Listen closely and you’ll hear it’s not quite the same. There is weight, density, and grit in the second example. 

To illustrate the difference, here’s all the added distortion isolated, so you can hear what we’re introducing into the signal with this preamp gain control besides the level boost:

That is a whole bunch of distortion. So yes, this gain knob affects sound quality.

Now, if we switch the compressor in, this added gain is absolutely going to affect the sound, even if we compensate for it with the gain controls in the compressor section.

Hear the difference? One is obviously more compressed. In effect, we have incorrectly gain-staged into our compressor circuit.

Even though the level of the two examples is roughly the same, we are feeding the compressor with a much stronger signal in the "after" audio example, and so the compressor reacts with more intensity than it would to a signal of lower gain.

This is an example of adding gain at an incorrect place in the signal chain. It is also an example of both gain staging and signal flow, which we’ll explain now. 

Gain stages and signal flow

Gain stages refer to specific points in the audio signal chain where the signal level can be adjusted or manipulated. In the plugin shown above, the preamp gain, makeup gain, and channel gain are all gain stages for the signal. Each one serves a particular purpose, has its own tonal variation, and contributes to the overall signal processing.

Signal flow, on the other hand, refers to the path that the audio signal takes through the different components in an audio system, from the inputs to the busses, auxiliary channels, and outputs.

Gain stages are like sluice gates in a canal, regulating the strength of flowing water. Signal flow is the water itself.

Tips for setting gain levels

A whole article could be written about gain staging. In fact, we wrote an article on gain staging that you should read, as it gives you great tips for setting gain levels.

Always remember to test any plugin’s gain stage points to see if any of them add harmonic coloration. You can do this with third-party software like DDMF Plug-in Doctor, or with your own ears: listen to the sound of the circuit cranked, level-matched to the signal at unity gain (nothing being touched).

In fact, you should always level-match your before and after comparisons. This will help you make sure that the color you’re adding is intentional. Many plugins offer level-matching options. Many also offer clean output controls that don’t affect the signal’s coloration. Still, you should learn how to do this with a meter like iZotope Insight.

The order of operations is simple here: play the original sound for three seconds while watching the RMS level and Short-Term Loudness level in the meter. Note the average numbers you tend to see here. Make your changes, and then use a clean gain attenuator (a plugin like Relay, sitting after the plugin you’re actively manipulating) to bring the level down till it matches the numbers you got at the beginning. 

Now you can a/b the sound as you switch the clean gain attenuator in and out. This will give you an accurate appraisal of whether or not the sound is better.

Start understanding gain in audio

Achieving the right gain levels can be difficult because it depends so much on the sound in question and what you’re going for. In general, you want a healthy level that doesn’t have too much hiss from the noise floor (the sound of the electrical components, rather than the sound of the music). You also don’t want any gain stage to introduce obvious distortion—unless, of course, you do. That’s where it gets tricky.

Your investigation into this topic is hardly over. You need to read more on gain staging to inculcate some other essential terms into your noggin (clipping and headroom, for example). And above all, you need to get out there and practice. So do that!

And if you're looking to experiment with gain, check out the Lindell Audio 50 Series and try these gain techniques yourself.

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