Pre fader, post fader. The difference has to do with the fader position on any given track (shocker) and is especially relevant when using aux/return channels. If you don’t know the difference, you’ll be sending a very different amount of signal to your aux channel than you likely intend which can cause problems or at least unexpected results in your mix. Let’s explain the difference between pre fader post fader now.
Pre Fader Post Fader Explained
I just mentioned that the difference between pre fader and post fader is especially relevant when using aux/return channel. An aux channel/track (also known as a “return” channel in my DAW, Ableton Live) creates a channel which you can blend into any given track in your mix.
A common use of aux channels is when using spacial effects like a reverb or delay. Drop a reverb on an aux channel and you can turn up the respective send dial on any track to blend in a wet reverb signal with that track. Aux channels save processing power and allow you to feed the same instance of an effect to every track in your mix at varying levels.
You’ll note that there’s a setting next to every aux channel which reads “pre fader” and “post fader”. Selecting one over the other determines the “input” level of that track for the aux channel.
While you still blend in how much of that “wet” effect via the send knob for that track, the degree to which that knob will add that effect will vary depending on the input.
Setting an aux channel to “pre fader” means that it uses the volume at the end of the signal chain for every track as their inputs, regardless of their fader positions. This is the level of gain at the end of the signal chain after all your inserted effects on that track.
Conversely, setting an aux channel to “post fader” means that it will go by the fader volume as the input.
As such and when using post fader, depending on where you have the fader set, every track could end up with a much higher or lower input for the aux channel.
Pre Fader Post Fader Example
Let’s give a practical pre fader post fader example to explain which is better to use.
Let’s use the reverb aux channel as an example. You can obviously put any kind of effect you want on an aux channel, but reverb is a common and useful choice.
We create an aux channel (again known as a return channel or track in Ableton Live) in our mix. We drop our reverb of choice on the aux channel.
Now let’s apply it to a vocal track in our mix.
We set the aux channel to pre fader and turn the send knob up until we get a blended amount of wet signal from that reverb which mixes well with our dry signal.
We’re happy with the balance and move on.
Later through the course of mixing, we decide the vocal needs to come down a bit.
We turn down the fader a couple dB. The dry signal is now quieter, but with pre fader on the aux channel, the wet signal of the reverb remains constant.
Now the reverb is too noticeable and that blend amount we nailed before is off.
We can fix this by turning down the send amount, but we wouldn’t need to do this had we set the aux channel to post fader. Had we done that, our adjustment of the volume of the dry vocal via the fader would’ve also brought down the wet signal.
With post fader, again the wet signal is essentially chained to any fader adjustments we make.
Get the perfect blend of dry and wet with the send knob, then if we decide later we need to turn the track down, we can adjust the fader and the wet reverb signal comes down along with it.
Just as an aside, personally I like to do my level automation using a utility plugin at the end of my signal chain for each track (speaking of which, this is a good time to mention my recent gain staging cheat sheet).
One last thing to mention in how pre and post fader affects your mix.
With post fader, turning the fader all the way down to effectively mute that track will also mute the send as its tied to the fader. If you have it set to pre fader and your turn the fader all the way down, you’ll still hear (exclusively) the wet instance of the track.
Sometimes you want this as this can create an interesting aesthetic effect to hear purely the 100% wet instance of that track. Other times you might feel like you’re going crazy not knowing where that signal is coming from.
It’s probably obvious to mention, but still worth considering that as a detail in the differences between pre and post fader.
Which to Use Pre or Post Fader?
While I recommend post fader because it uniformly moves the wet signal up and down with the fader, the more important thing is to commit to one over the other at the start of your mix and mix accordingly with that setting in mind.
Going back to that earlier example, if you decide you need to turn down the faders for all of the tracks in your mix uniformly at some point, the wet dry balance will be off with pre fader.
You can insert a gain plugin at the end of your signal chain to effectively act as a fader but before the fader (pre fader), but that’s not as convenient as simply turning a fader up or down.
Pre or Post Fader Reviewed
- Pre fader and post fader dictate the input signal of a track as it relates to an aux/return channel in your mix.
- Pre fader means that the aux channel uses the level of a track at the end of its signal chain as the input. It ignores the fader completely with this setting.
- Post fader means that the aux channel’s input for any given track is determined by its fader position. Turn the fader up and the input for the aux channel goes up. Turn it down or completely down and the input goes down or mutes completely, respectively.
- Amount of that wet signal via the aux channel is still affected by the send knob amount for any given track, but that input will have a direct impact on the send knob.
- In other words, more input means the send knob sends relatively more wet signal. If you have next to no input for that dry signal, you will hear next to no wet signal.
- With pre fader, you can turn the fader all the way down and just hear the wet instance of the track via the send which can make for an interesting aesthetic effect in some instances.
- I generally recommend setting your aux channels to post fader so that they’ll come up or down in relation to your faders. This is the most natural and efficient way to use aux channels, particularly when it comes to quickly adjusting the volume of your tracks via their faders.