Pre-fader vs Post-fader Aux sends/return and Insert FX: How to use it?

Using Parallel or Serial Effects in the mixer

One common question: “When to use parallel or serial based audio effects/processors?

If you connect the effects in parallel, you have two kinds of signals: the “Dry” and the “Wet”. Dry is the original, unaltered audio signal while the wet is altered signal by the effects. So you can basically adjust the Dry/Wet ratio with parallel effects. Connecting effects in parallel results to having two signals combined signal (dry and wet). The amount of wet signal depends on the setting of the FX hardware connected in parallel.

A common example if the reverb (which is a parallel effect) has settings of 40%dry and 60% wet. Technically; the aux sends dry and then the aux return has some reverb signal which is around 60% mixed. Use parallel effects if you like to control a dry/wet signal response. Insert FX effects need to have one input and one output. The output is a direct function of the effect settings except if you bypass it.

In music production, the most popular application of connecting FX in parallel are the following:

a.) Using Reverb
b.) Implementing parallel compression to make bigger and powerful sounds of drum or other instruments.

Which one to use? Pre-fader or Post-fader

Another common question: “Which is better to use, Post Fader or Pre-fader Aux Sends/Returns?” It depends on your audio application. For example pre-fader is useful in situation where you would like to pre-monitor the output without yet adjusting the fader. Let’s elaborate. This is how the signal path when connecting in pre-fader:

Signal —- > FX in Pre-fader —- > Fader

Now if you send the output of the pre-fader to any monitoring equipments (your headphone for example), then you will only hear the outputs of the FX connected in pre-fader. If you increase the fader volume up or down, the output of the pre-fader is unchanged because it will not be affected by changes with the fader. The primary reason is that its output is not passing the fader. This is useful if you like to listen how the mix would sound like without adjusting the fader.

In post-fader connection, one of the most popular effects will be the reverb. This is connected in post-fader to correctly maintain the dry/wet ratio with corresponding changes in volume level. For details on this topic, please read this tutorial on how to use a reverb unit.

Looking back on the first screenshot on this article, you will only see one channel strip of an audio mixer. Real mixers have more than one channel strips (typically 8 or even 24-channels depending on the size of your mixer). All you need is to remember how one channel strip works in the mixer. Then you will know how you will be using the pre-fader and post-fader connections in your projects. Once you know this, everything else will be very easy and you can see the same channel strips throughout your mixing hardware.

Take note that the input audio to the channel strip is either coming from a microphone pre-amp. While the output audio is the resulting processed audio of all effects combined (sends or inserts).

This output can then be panned depending on its location in the stereo field. Finally if you are mixing 2 or more tracks (channels), the summation of each processed audio output from each channel will become the output to the main mix monitor (the main mixer output). Think of it like this:

Processed audio output (Channel 1 + Channel 2 + Channel X…) = Stereo Signal at Main Mix Monitor

Content last updated on June 28, 2012