Note (27-11-2012) : This article need some rewriting. It contains a few inaccuracies - especially in regards to the terminology used. Be careful with what is written here, but understand that the basic point being made is that Ableton under most circumstances has much more head room than I first thought. It will be rewritten in time, but please feel free to email me with corrections

Clipping In Ableton: How To Avoid It

If you've used any DAW, you've probably had questions about gain and clipping. In this article, I'm going to try to address the question of why clipping occurs, how to avoid it, and best practice for gain structure within Ableton.

Since I started using Ableton, I have held on to some naive assumptions about clipping and how it works. The assumptions I made affected the way I structured in gain inside Ableton. Then, yesterday a few questions arose in my mind about the way gain in Ableton works. I started asking questions and then my assumptions were turned on there head. I used to think that a red volume Meter in Ableton was always indicated clipping and was therefore a bad thing. It turns out I was wrong.

My Initial Assumptions

My initial assumption about clipping was that if any signal went above 0db anywhere in Ableton, clipping would ensue and that clipping would be carried along all signals paths to the master channel. I based this assumption on the fact that if a signal went above 0db, the volume meter for that part of the chain would go red. Red usually means bad. It turns out that this was incorrect.

When Does a Signal Clip?

It turns out that a signal will clip inside Ableton when
A) The signal goes above 60db or
B) When the master goes above 0db (red), or
C) A signal is brought in to Ableton from a 3rd party entity like a VST Instrument or Effect and that VST can not handle signals above 0db

So, the only hard and fast rules are to make sure that your master doesn't peak above 0db, that no signal goes above 60db, and that if you are using external instruments, effects, make sure that they are not clipping.

My Experiments

Thanks to some help from people on the Ableton forum, I was prompted to do some experiments. At this point, I was still clinging on to the idea that everything clips at above 0db, but what I couldn't understand is that when I turned the master fader down to a level where it was not clipping, I could not hear any clipping despite the fact that to the two tracks that I had mixed together were peaking at higher than 0db. The simple experiment is this:


Create a midi channel
Throw a sine wave operator on there and play a C3 in a loop
Turn the volume of the operator up to 5db
Set the track's volume fader to 0db
Set the master volume to 0db
Notice that the track's volume goes well in to the red, and likewise with the master's volume.
Notice that you hear clipping


Now, simply turn the master fader down by 5db
Notice that the track's volume is still well in to the red
Notice that the master volume is green
Most importantly, notice that you can not hear clipping.


Turn the Operator volume to 0db
Put two Utilities after the Operator and set their Gain's to 30db each
Set the master volume to -60db (turn your amp volume down just in case!)
Notice that the Operater track, and the two Utility's volumes are red
Notice that you cannot hear clipping


Turn the master track's volume down 2db to -62db
Turn one of the Utility's gain's up 1 db to 31db.
Notice the master is green but we hear some filthy-ass clipping going on.

Phase Cancellation Test


Flatten a track at 0db of operator at 5b down to a sample
Duplicate this track
Group the two tracks
Pan one track to the left and the other to the right
Turn the sample on one track down by 5db and turn that track's volume up by 5
Put a utility on the group and turn the phase up to 200%

Gain Structure

Previously, I had been meticulous about making sure that no devices along any chains went above 0db because I believed that this would cause clipping. I was also very scared that a mixed signal sent to the master at higher than 0db would cause clipping and that turning the master fader to anything other than 0db was a bad idea because clipping could occur without me knowing. These fears turned out to be unfounded. Does that mean I should abandon keeping everything in the green?

This is now a subjective matter. By that I mean, there's no hard and fast rule that requires you to keep everything in the green or to not simply turn your master fader down a few db in order to stop clipping at the master level. However, I still personally feel that leaving the master fader level 0db is a good idea because if you follow this rule, you will always be able to see the master channel's peak value in Ableton, and this allows you to know how much head room you have for mastering at any point in time. As for allowing any one device to go in to the red - that's up to you. Just remember, that it is theoretically possible that if you send a signal off to a VST that is peaking at higher than 0db, there is a chance that that signal may get clipped and then come back in to your mix.

Conclusion

This has been a real learning experience for me. I'm not sure if it will change any of my gain structure habits, but it's certainly taught me not to take anything for granted. My assumptions seemed reasonable, and other people had told me that red meant clipping, but it turned out to be wrong. Always take the time to test this stuff for yourself use your own judgement. Critical thinking is probably the most important aspect of facing the challenge of becoming a good producer.

References

Although, forum posts are not really great references, I'm leaving them here so that people can see how I and other people went about asking this same question and how the question was answered. If you are skeptical of any of this, please experiment for yourself and send me the results.


The thread I started
The Ableton thread where this was already answered
A Gearslutz thread (post 24 onwards)

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