What is gain staging and why is it important?
Gain staging is the process of managing audio volume levels through the processing chain, from input to output. It prevents digital distortion, preserves dynamic range, enables proper signal processing, and ensures a mix for optimal sound quality.
Digital Distortion (clipping)
In the digital world, the loudness ceiling is 0 dBFS, if the volume of an audio signal exceeds 0 dBFS then it will distort or clip, resulting in unwanted noise and dynamic changes to the signal. By digitally clipping a signal you are rounding off the waveform which creates uneven higher frequency artifacts.
To better understand this, let's consider the analogy of transforming a smooth sine wave into a square wave. A sine wave exhibits a pure, rounded shape, when we apply digital clipping, the rounded peaks of the sine wave get chopped off, resulting in an approximation of a square wave. This alteration significantly changes the tone and introduces additional harmonics that were not present in the original signal.
Illustration of a clipping signal (digital hard clipping)
Avoiding digital clipping is crucial for maintaining audio fidelity. It involves careful management of the signal levels during recording, mixing, and mastering processes. By staying below the 0 dBFS threshold, audio engineers can ensure that the signal remains within a safe range, preserving the integrity and dynamics of the sound.
Digital distortion vs analog Distortion
"Guitarists use distortion all the time!"
There is a huge sound difference between analog distortion and digital distortion. Digital distortion often has a harsh and unpleasant quality that can significantly degrade the audio. It can introduce artifacts and unwanted digital clipping, resulting in a broken-up distorted sound that lacks musicality. The degradation caused by digital distortion is typically more evident and can be perceived as "ugly" or unnatural.
On the other hand, analog distortion can achieve desirable effects. It offers a range of sonic possibilities beyond just making the sound louder. For instance, analog distortion can enhance sustain on an instrument, add harmonic excitement, provide compression, and infuse the sound with punch and grit. Unlike digital distortion, analog distortion tends to be more gradual and organic in nature.
What is gain staging?
"I don’t need to gain stage, I can just turn down the master volume" Wrong, and I'll tell you why.
Gain staging is ensuring your audio signal doesn’t clip at any time throughout its path from the input to the master output. This includes potential clipping within any of your plugins and effects units. Turning down the master volume doesn’t eradicate any clipping or digital distortion that may have happened prior to the signal reaching the master channel.
To illustrate the importance of gain staging, let's consider a scenario. Imagine you are using an audio recording that you have processed using a VST chorus plug-in followed by a compressor plug-in, the output of the chorus mixed with the original signal has caused the volume to peak over 0dBFS, this signal is then fed into the compressor, the compressor then reduces the peaks lower than 0dBFS. The master volume will not show it's clipped, however, digital distortion has still happened on the output of the chorus and at the input of the compressor. This can result in unwanted digital distortion and compromised audio quality, even if the master volume appears to be at a reasonable level
How to gain stage
"The difference between the audio signal and the loudness celling (0dBFS) is known as headroom"
The easiest way to gain stage is by setting the input gain to a level that will allow you to process the audio through multiple VSTs and audio effects without the output ever reaching 0dBFS.
I have highlighted some key steps to ensure optimal audio quality and prevent digital distortion;
Set the Input Gain: Start by adjusting the input gain of your recording device, audio interface, or sound source. This ensures that the incoming signal from your source is at an appropriate level. Aim to capture a strong signal without causing any clipping or distortion during recording.
Maintain Headroom: Headroom refers to the difference between the audio signal and the maximum loudness level represented by 0dBFS (decibels Full Scale). It is recommended to keep the volume lower than -6dB throughout the entire signal path. This allows sufficient room for processing and lessens the chance of the output reaching 0dBFS. By leaving this headroom, you ensure that your audio has space to breathe and avoid unwanted clipping.
Gain staging: When working with multiple tracks in your DAW (Digital Audio Workstation), pay attention to the levels of each individual track. Adjust the faders or gain controls to achieve a balanced mix. Avoid pushing the levels too close to 0dBFS, as this can lead to clipping when the tracks are summed together.
Use Gain Plugins or Trim Controls: Within your DAW, utilize gain plugins or trim controls on individual tracks if necessary. These tools allow you to make fine adjustments to the levels without compromising the overall sound quality. They can help bring the levels of different tracks into alignment while maintaining headroom.
Consider Bus and Group Levels: If you're grouping tracks together or routing them to buses for processing, ensure that the combined levels of these groups or buses are appropriately balanced. Again, avoid excessive levels that can cause clipping when summed together.
Monitor the Master Channel: Keep an eye on the level meters of your master channel throughout the mixing process. The goal is to prevent the master output from hitting 0dBFS or beyond. If you notice that the overall levels are too high, use fader adjustments, gain plugins, or bus levels to bring them down while maintaining the desired balance and clarity.
Pay Attention to Frequency Conflicts: When two sounds—such as a kick and a bass—share the same frequencies, they can potentially sum together and create frequency volume spikes. This can lead to the master volume exceeding 0dBFS. To address this, consider using techniques like sidechain compression or EQ adjustments to carve out space for each element and prevent excessive volume buildup.
By following these steps and being mindful of your signal levels throughout the entire production process, you can achieve proper gain staging. This helps maintain audio quality, prevent digital distortion, and ensure a clean, professional mix that translates well across different playback systems.
32-bit floating point
Does 32-bit floating point stop clipping?
With 16-bit and 24-bit, if your signal clips when you bounce down to audio, then there is no way to unclip the outputted audio file. Whereas 32-bit floating point can act as a safety net for producers who are lazy with gain staging, it can give you extra headroom if the audio input has remained digital. This means if you bounce down a midi-driven VST at 32-bit floating point, then the non-clipped audio can be restored.
This doesn't work with analog inputs or clipping of analog sources such as an audio file. So it will not help to clear up a recording of an instrument that has clipped on the input, or with an audio file or sample which has clipped through the signal chain.
Ultimately, gain staging is the best way to ensure your audio remains clean and artifact-free.