The Untold Secrets of Clean Audio: Signal Flow & Gain Staging
Would you believe me if I said this is probably one of my favorite topics? One of the reasons why is because so many people out there have a really hard time understanding this topic and I can talk about it for hours trying to explain it. Signal Flow & Gain Staging are some of the most important topics in audio and very rarely do I see producers and engineers talking about it. As if you're expected to just know. So without further ado, Let’s dive in!
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10.1 Understanding Audio Signal Flow
- Defining signal flow and explaining its importance in recording and audio processing.
Ahh, Signal Flow. “if you pour water into a pipe, it will come out the other end”.
If you think of this analogy whilst we discuss signal flow it will make things easier. Because if you put audio in, audio will come out somewhere else.
We’ve discussed i/o in our audio interface lesson. An input is where our audio devices such as Mics and Instruments plug into the interface. The output is where the speakers would connect, allowing us to play sound out of the interface and into the speakers. But what about inside the DAW?
Well my friend, this is where the fun begins. Once the audio travels through your interface and into the DAW it travels a singular path. That path is what you make it to be. Where acoustic energy (sound) in the world around us can seem omnipresent, once that acoustic energy is converted to Audio (electricity in the computer) it needs a defined path to travel as it makes its way through your interface, the DAW, and then back out to your speakers where it's played back as acoustical energy again.
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- Cover basic audio paths: input, processing, and output.
At the beginning, a microphone captures your voice as acoustical energy or ‘sound’. A microphone is a “transducer” it converts or transduces acoustical energy into electrical energy or audio. This electrical energy or audio is sent to an audio interface. The audio interface converts this electrical energy (audio) into binary which your computer understands. Now even though it’s been converted to binary, we can continue to think of it as that electrical energy.
So we’ve now transduced acoustical energy into electrical energy (acoustics into audio). Now we get to “process” the audio. Processing is adding effects and manipulating the audio to alter its sound. We’ll cover the different effects in the next lesson.
In the midst of our processing, each new effect is like a new pipe in the water line. The audio travels through these pipes in a single-file fashion.
The order in which you place effects changes the way audio behaves.
Again for those in the back. The order in which you place your effects DOES change the way the audio is processed. While we won't get into the nitty gritty just yet, this is absolutely important to understand.
For example: Let's imagine we are painting a picture. We have a white canvas, green paint and black paint. Order of operation here is important.
If we paint the whole canvas black, we can no longer see any white. If we paint a green line, the green will be on top of the black which is on top of the white that we cant see anymore.
If we were to paint the whole canvas green, and then a black line on top of the green. We would see a black line on a green canvas which is completely blocking the white.
This same concept is applied when processing audio. The signal our microphone picks up is analogous to the white canvas. It's the pure unadulterated base from which our painting can begin. We can then apply different colors or effects to - change the way the canvas looks - or, how the audio sounds.
This is Signal Flow. The order in which the audio is processed or “the order in which you apply paints”.
As a teaser, Using an EQ before a compressor will compress what you EQ. Using an EQ after your compressor will change the dynamics of the compressed signal. More on this later!!
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Signal Flow Example:
You can also think of signal flow as “stages”.
Stage 1 = input
Stage 2 = effect 1
Stage 3 = effect 2
Stage 4 = effect 3
Stage 5 = output
The audio signal travels through each stage in a single file line. Each stage the audio goes through is layer on top of one another until you get the final product which is then played out of your speakers.
Also, don't take this as in “you need” to apply effects. In reality, the less you affect the audio the cleaner it will be because the less it has been processed.
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10.2 Gain Staging
- Explaining the dB and Gain Staging in simple terms, Understanding how to manage audio levels.
Remember those stages we just talked about? This is where the magic of Gain Staging comes into play. Each stage can/ will change the gain level.
What is Gain?
Gain is, and is the adjustment of, the dB level at which an audio signal both Enters and Exits a device. Gain allows the user to adjust the dB level. I have a whole in depth lesson on what the dB is and its role in audio (Here).
For this lesson’s clarity, the dB is the measurement of the audio’s “level” from inaudible (-100dB) to pushed past the computers limits (0dB and above).
If the audio enters an effect at a level of -20dB and it exits the effect at a level of -15dB. This indicates that your processing increased the gain of the signal by +5dB. So what does this mean?
If your processing affects the Gain level or Gain Structure, you’ll want to compensate in whichever way it went. In our example above, our signal increased by 5dB. This means we should lower the output gain by -5dB so that it leaves the effect at the same level that it entered the effect. If it were to reduce the overall gain level by 5dB we would want to increase the output gain to adjust for this reduction. Compensating by increasing or decreasing the output gain in order to match the input gain level.
This is the art of Gain Staging.
Almost every effect will have an Input gain knob and an output gain knob. This allows the user to adjust the level of input and the level of output in order to maintain a solid gain level at each “stage”. Input is a stage and Output is a stage. Wherever gain can be altered is considered a stage.
Let's add some numbers to our 5 stage example from above.
Stage 1 = input > -20dB
Stage 2 = effect 1 > adds 5dB of gain
Stage 3 = effect 2 > adds 10dB of gain
Stage 4 = effect 3 > adds 5dB of gain
Stage 5 = output > a total dB level of 0dB
In this example we’ve added a total of +20dB to our original input signal and by the time it reaches our output signal it hits 0dB which means its clipping! This is bad! It means we are distorting the audio because the gain is too high! We need to compensate for the increases in gain from our processing.
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Let’s try that again, but this time, with proper gain staging techniques.
Stage 1 = input > -20dB
Stage 2 = effect 1 > adds 5dB of gain > you use the output gain knob to reduce the gain by -5dB
Stage 3 = effect 2 > adds 10dB of gain > you use the output gain knob to reduce the gain by -10dB
Stage 4 = effect 3 > adds 5dB of gain > you use the output gain knob to reduce the gain by -5dB
Stage 5 = output > a total dB level of -20dB
Now our audio signal stays the exact same through the entire effects process! This means that the audio signal leaves the output at the same level as it came in. This prevents our Gain from creeping up louder and louder as we process our audio as though we never really processed the audio in the first place.
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Why is this important? Let's use the same examples as above in combination with our new understanding of signal flow.
Stage 1 = input > -20dB
Stage 2 = effect 1 > adds 20dB of gain and exits the effect at 0dB ‘clipping’ the audio > you don't turn it down
Stage 3 = effect 2 > will receive a clipped/ distorted audio signal from the jump. Reducing the gain here won't help anymore > it also increases the signal by 5dB.
Stage 4 = effect 3 > receives a hot +5dB signal that sounds destroyed by distortion and is beyond helpless. > it also adds 5dB
Stage 5 = output > a total dB level of +10dB and you’ve absolutely destroyed the quality of your audio.
Had you turned down the output gain at stage 2 by -20dB you would have saved your audio signal from sending stage 3 a clipped signal. This affected the way stages 3, 4, and 5 received all of their signals. It compounded in a very nasty way. The best practice is to maintain the same Gain level throughout the entire chain of stages. If you’re distorting the audio signal and you add another effect, you’re adding an effect to a distorted signal and not the clean one. If you manage the gain levels but in and out of your effects, you’ll maintain a clean signal throughout the whole process!
Gain Staging is crucial to the integrity of your audio throughout the signal flow.
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Summary:
Signal flow and gain staging are critical but often overlooked fundamentals in audio engineering. Their importance for maintaining clean and professional audio quality is often understated.
Signal Flow
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Audio Stages: Input (e.g., microphone capturing sound), processing (effects applied in sequence), and output (e.g., speakers). The order of processing effects directly impacts the final audio result, much like painting a canvas in layers.
- Key Takeaways: The sequence of effects matters; applying them thoughtfully ensures audio remains clear and dynamic.
Gain Staging
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Definition & Role: Gain refers to the decibel (dB) level adjustments made at each stage of the audio path. Proper gain staging ensures consistent audio levels, preventing distortion or clipping.
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Process: Every effect in the signal path can alter the gain level. Adjust input and output gain knobs to maintain consistent levels through all stages.
- Impact: Mismanaged gain staging can compound issues like distortion across stages, degrading audio quality. Correcting gain at every step preserves signal integrity and fidelity.