Tracking with Dynamics Processors in Logic Pro

With 24-bit digital recording and better analog to digital converters than ever before, is there any point using dynamic processors when recording? Mike Watkinson examines the benefits.  

It is common practice for recording engineers to use dynamic processing while recording. This originates from the need to maximize the signal-to-noise ratio and exploit the headroom available when recording to tape. With 24-bit digital recording and analogue to digital converters giving better than 120 dB signal-to-noise ratio, this is no longer a priority. However, compressing "on the way in" and using a noise gate to maximize the potential of that compression is still seen as good practice. This is partly to control the dynamic range and prevent clipping of, say, an over-enthusiastic vocalist. The benefits are also felt when mixing: Applying severe compression at the mixing stage only because the performance is "too dynamic" can reveal the less than pretty sonic performance of cheaper plug-ins (such as those that come free with your DAW!).  Light compression during tracking, followed by light compression when mixing can achieve a similar reduction in dynamic range without pushing either compressor into its red zone. 

In Logic Pro

If you had enough money you could purchase hardware dynamic processing for every channel that you wish to record when tracking (or buy an SSL). Simply adding effects, such as a noise gate or compressor to an audio channel in Logic Pro will affect the audio you can hear, but not what is actually recorded. Don't forget that Logic's effects work in real-time and you will be listening to the output of each channel, not the signal that is being recorded. You can prove this by recording audio through an audio channel with plug-ins inserted and active then, after recording, bypassing them; the sound you hear will change.

The plug-ins on this audio channel will have an effect of what you can hear, but not what is recorded

The plug-ins on this audio channel will have an effect of what you can hear, but not what is recorded

It's All in the Routing

To set up Logic's Mixer so that you can record the effect of inserted plug-ins follow these steps:

  1. For each audio track onto which you wish to record, create an auxiliary channel strip (click the plus button on the left hand side of the Mixer or press Option-Command-N with the Mixer in key focus)
  2. Connect the input of each audio channel to an available bus
  3. Connect the output of the auxiliary channel to the same bus. 

The signal enters the Aux channel and is then bussed to the Audio channel to be recorded

The signal enters the Aux channel and is then bussed to the Audio channel to be recorded

If you connect the output of the auxiliary channel before connecting that bus to the input of the audio channel, Logic will automatically (and confusingly, in this case) create an additional auxiliary channel. So make sure you do this in the right order!

One disadvantage to the way Logic adds channels to the Mixer is that the auxiliary channel is added to the right of the audio recording channel. For those who prefer their signal path to flow from left to right, this is the wrong way around. To swap the order of auxiliary and audio channels, right-click on the auxiliary track's header and choose '

Mike has been obsessed with music software since he first saw Fairlight's Page-R, and has tracked its development through his work as a performer, composer and producer. As a writer he has contributed articles to Sound On Sound since 1999, and currently writes their Apple Notes column. As well as being a certified Logic Pro and Pro Too... Read More


Yuval Rakavy
What is the benefit in input compression using DAW plugin. If there is a clipping, the clipping is in the A/D component, and compression will not help.
Yes, that is true, however input dynamics processing does allow you to control the dynamics of the audio captured to disk.
Couldn't you just create an input channel strip in the Environment mixer and insert the compressor on it? No need for extra aux tracks.
Yes - you could also use the environment mixer, but many users have never even opened it, as it is not part of the main arrange window. The environment mixer is a powerful place - but perhaps demands a tutorial series of its own.
Magic Fingers
i 2nd that for a tutorial series on everything Environment Mixer... I am one of those users who's barely given the EM any sunlight, but i have seen enough vids lately that have me wanting to tackle it. will search through some of the LogicNinja's old videos to see what i can come up with until then.
@Magic Fingers

What exactly would you like to know? Specifics on the Mixer layer in the Environment (which is very similar to the standard Mixer) or more about the Environment in general?

Another vote here for an entire 'Environment Window/Mixer' tutorial series. I never touch it, in fear of screwing something up.
Your wish is our command... ;-)

We've over 1,200 article on the MPVHub - so much stuff... so do use the search bar for The Hub (not in the search tutorials top bar, which will show video course results).

Now that's what I call service!!
Why thank you! :)
Magic Fingers
Thanks Rounik!

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