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If you’ve bought yourself a mixing console, microphone preamp, or even a condenser mic, you may have noticed the gain control knob on the control panel of your digital audio workstation and wonder what it does. A lot of people confuse gain control for volume control, but gain and volume have quite different roles when it comes to recording and how they affect your sound quality.
Wondering what microphone gain is and how it can affect mic signals? Here’s everything you need to know.
Talking, singing, or playing an instrument into a microphone causes minuscule vibrations in the diaphragm that are converted to electric signals. However, those signals have an extremely low voltage and need to be amplified.
The main use of microphone gain is to adjust the mic so that it has an equal signal strength closer to the nominal line level. Microphone gain increases the amplitude of a microphone signal, and the gain boosts signal strength from mic level to line level signals, so the microphone signals are compatible with professional audio equipment. Mic preamps control gain and are the first circuits a signal passes through after the mic output.
In other words, gain control is an electrical circuit that the audio signal passes through after leaving the microphone, and adjusting and using it correctly will provide a clear sound when you are recording or for those listening. It will also improve the tonal quality of your audio.
Making a gain adjustment can drastically alter the tone of your audio signal, and your audio interface will react differently depending on how high or low you set your gain. This can be most commonly seen in guitar amplifiers. Most guitar amps have a volume knob and a gain knob, with the latter on the guitar amp being used to change the voltage going in to get distortion.
Without gain, you wouldn’t be able to use the mic signals with other audio equipment, as they’d be too weak and result in a poor signal-to-noise ratio. The exact amount of gain needed depends on the microphone’s sensitivity – or the signal output per sound pressure level – as well as the sound level and distance of the sound source from the mic.
Because gain control is often explained as increasing or decreasing mic signal strength, many people mistake this to mean adjusting volume. However, these two are very different from each other.
The word gain is sometimes used as a reference to volume due to functions labeled ‘makeup gain’ on a compressor. This refers to an adjustment to compensate for the output volume but has been given another name.
Gain control is used to boost the line input signal up to line level signals. Microphone gain controls how loud the line inputs of the microphone to the channel or amp are. Line level is also considerably stronger than mic level signals, so you need to significantly boost the mic level signal to make them compatible.
Microphone gain refers to a boost in the amplitude of the microphone signal and is used because the mic itself produces weak microphone signals to get it up to par with the input signal of other audio sources.
Any adjustments made to make sound on the microphone louder after that is to be made using the microphone volume control. Microphone volume controls how loud the output volume of the channel or amp is. These details show the distinct difference between gain and volume and should help you understand how to control gain adjustments.
Now that you know the basics of what mic gain is, it’s important to understand gain staging and how much this can affect your recording. Gain staging is used to create level consistency in a digital system.
The idea of this is that the level going into the digital channel matches the level going out of the channel. Gain staging ensures that we’re using the optimal level going into our plugins, which can help us craft more accurate mixes and perceive our sounds better.
The gain of the mic preamp provides the boost that the input signal needs to get it to line level, and this can occur when gain is applied using mic inputs like a preamp inside the microphone body, such as in active mics. These need an external power source such as phantom power, batteries, or a USB mic.
Some active microphones are also fitted with attenuation pad switches, which decrease the signal’s amplitude of the output signal to prevent distortion, which could be caused by overloading the mic if it was positioned next to something like a kick drum. USB and digital mics also have enough adjustable gain to produce a signal that your computer needs for a quality signal level.
On the other hand, If a mic doesn’t have an active preamplifier, gain can be added by using separate or standalone preamps like mixing consoles, digital audio workstations, audio interfaces, and other audio devices. We’ve seen that microphones output mic level signals, and we’ve also seen that they require gain to make them compatible with line level.
Microphone preamps will give you this gain, but you should also keep in mind that the preamp signal is going to line input and not a mic input. Standalone preamps can also be connected up to a DAW through a digital interface or analog to digital converters.
Understanding what the microphone gain on your audio interface is and how gain and volume are different from one another may sound incredibly basic, but it’s the first step to being that much better when handling professional microphone equipment, even as an amateur.
Learning about how your sound source, audio signals, electronic signals, and other aspects interact within your mic can make quite the difference when adjusting gain to get the best audio you can.
If your gain is too low while recording audio, you will end up with a low SNR ratio, which will impart a lot of noise in your signal path. Your system won’t get the voltage it needs to convert your analog signal into a high-fidelity digital signal that your computer can use.
By most professional standards in recording, -18dBFS is a good average level and signal strength to aim for. Keeping it conservative will help you maintain proper gain structure throughout your mix.