If you’re wondering what microphone gain is, you’ve likely noticed the gain control knob on your preamp or mixer.
Or perhaps you’re wondering what the difference is between gain and volume.
Or how to correctly set gain for the best possible sound quality.
Or you’re wondering what mic boost is and how it relates to gain.
Whichever it is, you’re in the right place.
These are all common questions and we actually get a lot of messages asking them. That’s the reason for this article.
I will explain what gain is and what makes it different from the volume setting. I will also show you how to correctly adjust the gain to get the best possible sound. Finally, I will cover microphone boost, which is related, but different.
What Is Microphone Gain?
As covered in the articles on condenser mics and dynamic mics, when you talk, sing or play an instrument into a microphone, it causes minuscule vibrations in the diaphragm that are converted to electric signals. Those signals have an extremely low voltage—far too low to be useful. So they need to be amplified, in many cases to more than 1000 times their original strength.
This amplification in the signal is basically a “gain in voltage”, which is where the term “gain” comes from. To simplify everything (please don’t write me angry mail for this simplification—if you know the full technical explanation, what are you doing reading a post that defines the term “gain”?) the gain basically makes the sound from the microphone louder or softer. But it is not the same as volume, which I will cover below.
On a mixer or a preamp, the gain is the first control that affects the raw microphone signal. It functions to boost the signal to a strong enough level to allow the rest of the controls to have an effect. On a guitar amp, the main function of the gain is to create distortion. I go into detail on how to properly set the gain below. First I want to cover the difference between gain and volume.
Gain Vs. Volume: What Is Microphone Volume?
The main thing to remember here is that gain controls the input, whereas volume controls the output. You generally want to use the gain to boost the input signal up to line level. Then you don’t touch it again. Any adjustments you make to how loud the sound is after that, make them to the output using the volume control.
On a guitar or bass amp, the gain controls the level of distortion and volume controls the, you guessed it, volume.
How To Set Microphone Gain
As mentioned above, the gain control is the first thing to affect the raw mic signal and as such, it is usually located at the top of a mixer board. The goal is to set the gain level high enough to bring the input signal up to a normal level, but not so high that you get clipping and distortion.
Luckily, most mixers come with something called a Pre-Fader Listen (PFL) button. It lets you see the signal strength by using the LEDs on the mixer board. You want the to keep the signal just below the level where the peaks start to venture into the red. Once set, leave it.
On a guitar amp, setting the gain adjusts distortion, so the level you want it at comes down to personal preference. That said, many beginners tend to set the gain way too high (usually all the way to 10), thinking they are creating this amazing new sound. They’re not. Everyone has already tried the same thing and eventually learned that they sound much better with the gain a few levels lower.
Setting Gain On An Internal Preamp (In A Mixer, Etc.)
- Turn on the sound source
- Press the PFL button on the mic channel
- Adjust the gain until the meter shows a healthy level, i.e. large movement on the bars, but not venturing into the red
Setting Gain On An External Mic Preamp Connected To A Mixer
- Connect the output from the preamplifier to one of the line inputs on the mixer
- Set the line gain of that channel to 0 dB
- Turn on the sound source
- Press the PFL button on the channel to which the mic is connected
- Ignore the meter on the preamp and use the one on the mixer instead
- Set the gain on the preamp until the meter shows a healthy level (the meter on the mixer)
- More on setting up a preamp here
Setting Gain On An External Mic Preamp Connected To An Audio Interface
- Connect the output from the preamplifier to one of the line inputs on the interface
- Create a new channel and set it to record-ready; the meter will now show the level of the input signal
- Select the input to which the preamp is connected as the source for that channel
- Turn on the sound source
- Set the gain on the preamp so that the meter comes close to the top of the scale, but never goes ‘over’
Setting the microphone gain is really quite simple. You just have to make sure it isn’t too low or too high. If it is too low it will be closer to the noise level in the console or the digital audio workstation (DAW). This means that the signal-to-noise ratio would be too low and you would end up with more noise in the output than you want.
If the gain is too high, you could end up with clipping, which results in distortion. Thus, whenever you get clipping, you always solve it by lowering the gain, not the fader or something else. The signal is clipped at the gain control and adjusting anything after that is already too late.
Once you have the gain set correctly, you should not need to adjust it again, unless you make changes to the sound source, microphone position, etc.
Gain is not to be confused with boost, which is similar, but different.
What Is Microphone Boost?
Microphone boost also amplifies the signal from a microphone, but it is a setting found on a computer, not a preamp or a mixer. Usually, when you plug a mic into the computer, the volume is not loud enough for voice chat programs like Skype. To rectify this, you can use microphone boost to adjust the signal by +10 dB, +20 dB or +30 dB.
You can find the boost setting in the sound menu of the control panel. Once there, click on the ‘recording’ tab and find your microphone. Right click on it and select ‘properties.’ That’s where you will find the boost setting. You can also use the volume setting above the boost to fine tune the sound volume. In other words, if 10 dB is too quiet and 20 dB is too loud, set the boost to 20 dB and lower the volume 10 to 20%.