What Is Microphone Gain? – The Ultimate Guide

Martin Kristiansen

My name is Martin Kristiansen and I’m the founder and chief editor of HomeStudioIdeas.com. I’ve been playing, recording and producing music for the last 10 years.

Microphone gain is an important factor to consider when recording audio. Actually, adjusting gain is the first key step before you hit the record button. The amount of amplification that is applied to a microphone signal is used to adjust the level of the signal that is sent to a recorder. Too much gain can lead to distortion, while too little gain can result in a weak signal. This blog post covers everything you need to know about mic gain!

Let’s Start With The Basics

Before we dig into what microphone gain is, there are some basics we need to understand. More specifically, what sound is. I’m not a physicist, so I won’t go into heavy detail. But to simplify, sound is all about vibrations in the air.

Three things vibrate when sound is created:

As an example, when you hit a snare drum it starts to vibrate, making nearby molecules vibrate. They start bumping into their neighbor molecules, causing them to vibrate as well. If the vibrations are strong enough, they will be traveling through the air until they eventually reach your eardrum. When these vibrating molecules bump into your eardrum, it also starts to vibrate.

There are two important elements of the vibration: frequency and amplitude. The frequency is how fast the wave vibrates, and the amplitude is the size of the vibration. The higher the frequency, the higher-pitched the sound will be. Larger amplitude equals louder sound.

Amplitude is what’s relevant when we’re discussing microphone gain. When we increase or decrease the gain, we’re adjusting the amplitude.

So why is this important? By applying microphone gain you increase the size of the sound wave, making it louder.

But the most important thing is you’re also boosting the mic level to line level. This makes the audio signal compatible with professional-level audio equipment. We will talk more about how you apply microphone gain in an upcoming section.

Mic Level And Line Level

Every beginner has plugged in their microphone and started recording, and then wondered why the volume is so low. So what do you do? You increase the volume at the system’s output just to realize it has a ton of noise in it.

Why? You see, microphones record at what is called mic-level. To get a clean recording of your microphone, the low mic level signal needs to be boosted to line level.

Mic level

Microphone (mic) level is the voltage or signal of a microphone. This signal is usually around 1-5 millivolts (mV), while line-level is around 600-1,000 millivolts (mV). To make it useful, the mic level needs to be amplified to line level with the help of a preamplifier.

For simpler home studio setups, single-channel devices such as audio interfaces are the most common piece of equipment for boosting mic-levels to line-levels. If you’re recording multiple microphones simultaneously, mixers are preferred since they can include 14-64 input channels.

Line level

Line level is the voltage or signal strength at which audio equipment’s input and output functions. A line-level signal is approximately one volt or about 40-60 dB as strong as a mic-level signal.

Line level signals are also called “voltage signals” because they are transmitted and received as variations in voltage. Preamplifiers convert low-level signals, such as those from a microphone to line-level before the signal can be sent to a power amplifier and then to loudspeakers.

Why Don’t Microphones Output Line Level?

Truth be told, with so many devices on the market that amplifies mic-level signals to line-level, it would be unwise for traditional manufacturers to start developing XLR mics with built-in preamplifiers. There is so much gear available designed to do this, so why change the format now when it has worked for so long?

Also, USB microphones solve this issue by having two extra circuits: an onboard preamp and an analog-to-digital (A/D) converter. The preamp makes it unnecessary for the USB mic to be connected to a mixer or external mic preamp. 

The Definition Of Mic Gain

Microphone gain is a term used in audio recording to describe how much amplification the microphone is receiving.

Gain affects the overall quality of the recording. Too little gain and your recording will get a low signal-to-noise ratio, while too much gain will over-amplify or distort the sound.

Microphone gain works by adding energy to the low mic level. This is usually done through an AC wall plug, phantom power, batteries, or another source.

The amount of mic gain required can vary depending on the type of microphone being used, the sound quality you’re after, and your recording environment.

The gain is measured in decibels (dB) and can be either positive or negative, ranging from -10 dB to +5 dB.

Two ways gain can be applied to mic-level signals:

Gain From Built-In Active Preamps

Active microphones such as condensers have internal electronics and a custom transformer to boost the mic’s output level. To be able to function, they require something called phantom power, commonly designated as +48V or P48 on a mixer or an audio interface.

The extra voltage from the phantom power is needed to power the diaphragm and the mic’s internal amp. Remember, you still need to apply gain for active microphones such as condensers.

And then there are USB microphones. As previously mentioned, USB mics have built-in active preamplifiers and output digital audio. These built-in preamps usually have adjustable gain to effectively bring the mic’s audio signal up to line level before its converted to digital audio.

Since the built-in preamp has enough adjustable gain, all you have to do is to plug them into your computer and hit record.

Gain From Standalone Mic Preamps

Sound engineers prefer standalone preamps as they provide superior quality and it leaves more room for experimentation. There are tons of preamps on the market and each feature its own tonal qualities.

If you’re using a standalone mic preamp, make sure to connect it to the line output and not the mic input. You can also connect them to a DAW by using a digital interface or an A/D-converter.

However, the most common setup for bedroom studios is by using a USB audio interface. Many will feature two or more mic inputs, including built-in preamps.

How Does The Microphone Gain Affect Microphone Signals?

As previously mentioned, the goal when applying gain to a microphone is to boost it to line level. The amount of gain you’ll need to add depends primarily on three things:

As an example, condenser microphones are active with built-in preamps, making them more sensitive than passive mics such as dynamics. Because of that, condenser mics require less amplification from gain to achieve line-level signal strength.

Additionally, if the sound source is further away from the microphone, you’ll need more gain to boost the mic to line level. Remember, sounds are molecules vibrating and bumping into other nearby molecules. However, the vibrations will wear off for each molecule further away from the sound source.

Lastly, sound vibrations created from loud sounds have high amplitude. As we discussed in the beginning: when we increase the gain, we’re increasing the amplitude. As a result, loud sounds don’t require much gain to achieve line-level strength.

Mic Gain vs. Volume

When it comes to microphones, there are a few key things you need to understand to get the most out of your recordings. One of these is the difference between mic gain and volume.

Mic gain is the amount of amplification that’s applied to your microphone signal before any additional processing. It’s measured in decibels (dB), and it can be adjusted on most microphones or audio interfaces. As previously mentioned – the higher the mic gain, the louder the signal will be.

So what about volume? Volume is how loud the signal is after the processing. It’s measured in decibels as well, and it can be adjusted on most audio interfaces, mixers and music production software. The higher the volume, the louder the signal will be.

While the gain is the input dB, volume is the output dB. Ideally, you want to set both mic gain and volume as high as possible without clipping or distorting your signal after additional sound processing such as equalizers, compression, delay, or reverb, etc.

If you record with too little gain, the signal strength will be weak and you would need to increase the volume which leads to increased noise. With a high gain setting from the get-go, you can lower the volume without getting unwanted hiss and noise in the recording.

Tweaking the gain-knob also affects the tone and quality of the sound. Volume only affects loudness. You see, there is a maximum loudness inside of an audio system (controlled by gain) but there is no maximum loudness outside of the system at the output (controlled by volume).

Utilize Both Gain and Volume To Your Advantage

As you now know, gain and volume are two very different things. Still, people can sometimes use gain as a fancy way of saying volume. So when should you adjust gain and not volume? As a rule of thumb, increase or decrease mic gain when:

And use the volume knob in your DAW when:

What is Gain Staging?

Gain staging is ensuring the audio is set to an optimal level for the next processor in the chain. This is important because if the audio is too loud or too soft, it can cause distortion or clipping. By setting the levels correctly, you can ensure that the audio signal is clean and clear.

There are a few things to keep in mind when gain staging, including headroom and noise floor. 

Headroom is the amount of space between the peak level of an audio signal and the maximum allowed level. The noise floor is the background noise that’s present in any audio signal.

A good way to start adjusting the levels is by finding the loudest part of your track and making sure that it doesn’t exceed 0 dBFS (full scale).

By keeping these things in mind, you can properly set the levels for your audio signal and avoid any unwanted noise or distortion.

What is Automatic Gain Control?

Automatic gain control, or AGC, is a process used in audio engineering to regulate the level of an audio signal. This is done to keep the signal within a predetermined range, preventing it from becoming too loud or too quiet.

Automatic gain control is often found in streaming platforms like Discord, where it is used to ensure a consistent volume level for all users.

Essentially, AGC means no control over the gain for users. The software level out audio input quality on its own.

In music production and professional recording environments, you want to be able to adjust the gain yourself, making Automatic Gain Control undesired.

Frequently Asked Questions

How Does Gain Affect Recording Volume?

Microphone gain is the input signal strength. Therefore, increasing the gain will affect the recording volume at certain thresholds.

What Happens If My Mic Gain Is Too Low?

Recording with a too low gain creates a low signal-to-noise ratio. So what does that mean? The desired audio is too weak compared to the mic’s self-noise. The result? A recording full of noise and hiss from the internal electronics of the microphone.

What Happens If My Mic Gain Is Too High?

If you’re applying too much gain to the microphone’s signal, you’ll experience distortion and clipping. Distortion is an indication of too much power and can damage your recording equipment. It’s always best to keep the signal in the green area of your channel strip, with an occasional yellow.

Conclusion

Gain is the first knob to tweak when recording audio. By increasing mic gain, you’re amplifying the signal strength to line-level (0 dBV), making it compatible with professional-level audio equipment.

Unlike volume, gain affects the quality of the sound. Too little, and you end up with a low signal-to-noise ratio. You will also experience distortion and clipping if you’re applying too much gain to the microphone signal.

And there you have it – The ultimate guide about microphone gain. Let me know what you think in the comment section below.