Exploring the MASSIVE headroom in your DAW

David Mellor

David Mellor is CEO and Course Director of Audio Masterclass. David has designed courses in audio education and training since 1986 and is the publisher and principal writer of Record-Producer.com.

Tuesday January 29, 2019
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It is a common misconception that 0 dBFS is the maximum level that a DAW can handle. But in this tutorial we'll see that a modern DAW can go way beyond this.

This is a demonstration of the amazing amount of headroom that is available in a modern DAW. You might think that 0 dBFS is full scale, but within the DAW then much higher levels are possible.

It is important however to remember that if your input signal exceeds 0 dBFS on recording, or if your output signal attempts to exceed 0 dBFS on bouncing to a file, then clipping will occur. But within the DAW, the amount of headroom is truly amazing.

Let's start with a simple sine wave of 220 Hz peaking at 0 dBFS. You should turn down your monitors as it will be loud.

By the way, you will need to use a browser that supports HTML5 to see and use the audio player.

Here is what this looks like in the DAW. The sine wave has been routed to the left channel because this simplifies the demonstration rather than panning it center which creates a level change due to the pan law.

Original

The next step is to copy the sine wave onto another track. This is what it looks like...

Clipped

And, as you might guess from the red light at the top of the meter column of the master track, this is what it sounds like - significantly clipped...

At this point, it would be useful to consider where the clipping has occured. Did it occur when the two 0 dBFS sine waves were mixed together? Or did it occur on the final output to a .wav file?

Well we can find out easily by lowering the master fader by 6 dB. Two identical signals added together will raise the level by 6.02 dB. To remove the clipping it is necessary to lower the master fader by more than this, and in Pro Tools -6.1 dB is the nearest we can get. It looks like this...

Master minus 6 dB

And it sounds like this...

Yes, it's clean. If it doesn't sound absolutely 100% clean to you then it might be that the AAC encoding/decoding isn't quite as clean as the original WAV, which most definitely is clean. Or perhaps your audio interface is creating intersample clips that don't actually exist in the digital audio file. No problem - try out the test yourself in your own DAW.

From this we can see clearly that the clipping is not occuring within the DAW but only in the final output to an audio file. So this DAW has at least 6 dB of headroom above 0 dBFS. But maybe there's more...

+24 dBFS

OK, let's now go crazy with this and see just how much headroom Pro Tools has. Lets make some more copies of the sine wave. Each time we double the number of tracks, the level will rise by 6.02 dB.

Master minus 24 dB

With sixteen identical copies of the original 0 dBFS sine wave, we achieve a level of just a little over +24 dBFS. Wow. But by setting the master fader to -24.1 dB, the output is clean. And here it is for you to hear...

At this point we can definitely see that a modern DAW has loads of headroom. But perhaps there's more. What about this..?

+36 dBFS

Master minus 32 dB

Here we have 64 tracks all with the same sine wave at 0 dBFS. This adds up to a whopping 36.12 dBFS. But yet again, if we pull down the master fader to 36.2 dB, the output is clean...

Phew. That's probably far enough for this tutorial. This procedure clearly demonstrates that Pro Tools, as a modern DAW, has an internal headroom of at least 36 dB above 0 dBFS. How far it goes above that, well we'll leave that to your experimentation. But rest assured, only someone hell bent on recreating Frankenstein's monster could ever conceivably use 36 dB of headroom. For most of us 20 dB would still be way more than we would ever actually need.

So in conclusion, for all practical purposes we don't need to worry about clipping within the DAW, as long as the input is clean, and the output file is clean. This test doesn't take plug-ins into account of course, but that's another tutorial for another day.

Thank you for reading, and for listening.

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