Microphone gain is one of the most critical aspects to keep account of when recording. Without it, your mic would be virtually useless. But what exactly is gain and how does it work? Let’s dive in.
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What’s gain?
Basically, gain is the amount of amplification applied to an audio signal.
To break it down a bit further, gain refers to the extent by which your input signal is made “louder” or “quieter” before running into your interface or mixer.
Gain is normally measured in decibels (dB) and can be controlled by a knob either on your mixing console, interface, preamp, or sometimes even the microphone itself.
If you’re to imagine turning up the volume on your speakers, it’s basically the same idea. Except rather than adjusting the levels you hear, you’re adjusting the levels you record.
What’s the difference between gain and volume?
First, let’s acknowledge that some instruments have a higher output than others, thus making them louder. It’s not super-important to explain why this at the moment, since it can be for a wide variety of different and contributing factors. For now, just try your best to accept this as a part of functional reality.
Let’s say that we have two instruments, instruments A and B. Instrument A is louder, and instrument B is quieter. The purpose of gain is to compensate for instrument B’s lack of inherent volume. Meaning that if we were to run instrument B through an amp, we would have to set our gain higher so that the signal running through will be approximately equal to that of instrument A (which requires less gain). Make sense?
So, if gain determines how loud a signal is before it’s processed, volume determines how loud a signal is after. In layman terms, gain affects the quality of the sound, volume affects how loud it is.
Quick review:
- Gain is input level.
- Volume is output level.
- Gain affects quality.
- Volume affects loudness.
What’s the difference between mic and line level?
Mic level is the low-level signal that a microphone will output.
Microphones, for reasons we don’t have to get into right now, typically generate a weak electrical signal. This could be anywhere from a few millivolts (mV) to a few volts (V), depending on the microphone at hand and the particular sound source.
Mic level is usually very quiet and therefore requires amplification before recording.
Line level, conversely, is a signal that is of a much higher level. This signal can be anywhere from a few hundred to a thousand times stronger than that of a mic level.
With this in mind, it should hopefully be somewhat obvious that a mic level input has been designed to anticipate a mic level signal, and line level expects line level.
Sending a mic level signal into a line level will result in an extremely weak, noisy, and low level signal. Mic level inputs are generally designed with built-in preamps, so sending a line level signal into a mic level input will run the risk of completely overloading the input and potentially ruining your equipment.
How does gain affect sound?
If we understand that more gain applied to a microphone creates a louder signal, then it should be obvious that less gain creates a quieter one.
Many novices tend to assume that “loud is better” and will max out the amount of gain they’re adding to their signal flow, but this is a huge mistake. Gain can gradually affect your tone, and mass amounts of gain will begin to introduce noise and distortion.
When starting out, it’s important to make sure you’re adding enough gain to avoid your signal being inaudible and just enough to avoid clipping.
Getting comfortable with this process (known as gain staging), can help you to make informed decisions about why and how you set your gain.
What is clipping?
When an amplifier is given the task of delivering an output voltage or current beyond what it’s actually capable of, the effects of this is what we refer to as “clipping”.
We use this term because when pushed to its limit, your system will literally “clip” off the tops of your waveform. In other words, whatever audio was supposed to be there is permanently lost.
While clipping can be an intentional effect, particularly in heavier styles of music, it’s more often than not unwanted. After all, losing portions of your performance seems to defeat the purpose of recording it at all, does it not?
The best way to avoid clipping is proper gain staging.
What exactly is gain staging and how to do it?
Gain staging is the process of optimizing your audio signal levels at each stage in your signal processing to ensure that the greatest sound quality is achieved.
How to gain stage properly?
- Make sure you’ve set your audio source to a proper gain level. It should be loud enough to hear, but not loud enough to cause distortion.
- Adjust your preamp gain so that the signal is loud enough to hear, but not loud enough to cause distortion.
- Set your faders properly so that the signal is loud enough to hear, but not loud enough to cause distortion.
- Adjust your output gain so that the signal is loud enough to hear, but not loud enough to cause distortion.
General tips to help aid in this process
While different engineers have different preferences, a general rule of thumb is making sure that the loudest signal you anticipate on recording doesn’t reach above either -6 dB or -12 dB. This allows for a solid amount of headroom to help with postproduction.
- Try not to position your faders above 0 (if the audio was properly recorded).
- If your DAW’s meter starts to turn red, turn down the gain.
Gain-hungry microphones
There are microphones that require a lot more gain than others, largely due to their sensitivity or output levels being low. This can be a dynamic microphone with low output, a ribbon microphone, or even some condensers.
Notoriously gain-hungry microphones include the Electro-Voice RE20 and the Shure SM7B.
While it’s obvious that you’re not going to want to send too much juice into the signal, you may need to crank it higher than you would for other microphones.
A common issue that you’ll run into in a scenario like this, is that your interface or mix console won’t be capable of producing enough gain to compensate. If you find that you need to dial the gain all the way up for a decent signal, you’ll want to start to consider investing in a good mic preamp – or use a different microphone entirely.
Conclusion
While understanding microphone gain may seem like an overwhelming and complicated task on the outside look in, it’s ultimately a very basic principle of audio. Even a baseline level of understanding can vastly improve the quality of your recordings.
Knowing how much gain to apply, when to make adjustments, and what to avoid can allow you to record quality audio that’s easy to deal with in post.