Master Clipping issues

[Jera]

Hey Guys -

Anyone have an idea why the master bus clips but the output on a channel is not? I've been doing a little work around running leveler on the master and bringing down the volume but even just 1 channel of audio my master is clipping.

[buzzsmith]

Can't tell much from just looking, but I do see a clip indicator on your Key Bus and the master fader is +0.4.

And, as you most likely know, the outputs are cumulative. Meaning that an individual track does not have to clip but when they all are feeding the master bus simultaneously it's quite possible to clip the Master.

Buzzy

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[supersonic]

I second that. Put the master fader down to 0. Gain staging also is very important.

[TinenTech]

With 32-bit floating point internal processing, you can't "bus clip" in DP the way you can clip the summing amp of an analog mixer, but it's wise to keep old habits in mind. Every time you double the number of equally-loud*, non-clipping sources, the level at the master goes up 3 dB.

In an analog mixer, you'd have to cut back your channel volumes if you were clipping the summing amp. But in most digital systems, you can just pull back (or compress) the master fader…as long as the output meter never goes above 0 dBFS, it can't clip.


*equally-loud but non-correllated: if the signals are identical, the voltages add up, making a 6 dB increase.

[Shooshie]

Generally speaking, in digital audio, 0dB is really and truly an absolute limit. There are lots of tutorials out there which can tell you the whole story so you can understand why that's the case, and I recommend that you read them. It won't take long, and it's not super scientific or anything. (basically, you run out of 16 bit numbers to represent the volume, so it literally has no place to go)

However, DP and probably many other DAWs allow headroom above 0dB for the purpose of mixing. At 32bits floating point internal resolution it takes a LOT to clip your audio within DP. The red light merely tells you that you've exceeded the "real" maximum, that is, the limit for bouncing to CD at 16 bits.

So, we have a lot of freedom to disregard limits while we are working, but it's understood that when you leave DP and go analog (or bounce to CD) you will know to make sure that the audio output channels never exceed 0dB. Most mastering software for creating and burning CDs will do a clipping check and even "normalize" your audio (adjust it downward until all the clips are eliminated, within the 0dB range), but this is poor form and can seriously ruin your mix. You should have taken care of that back in the mix before outputting a two-track file for burning to CD.

There are SO many places where audio can take a leap or a dive, often without your being aware that it's even happening. Go through your audio chain carefully from input to output, studying every analog and digital connection, every plugin, every aux track, master track, fader, pan, and so forth until you are sure you know where everything is set, and how it is affecting the mix. It will make you a better, more thorough audio engineer.

Shooshie