What's the Difference: Pre-Fade vs. Post-Fade

Today, we’re back to our What’s the Difference series. These are going to be short posts where we look at commonly misunderstood terms in the tech world. Nearly every audio console offers aux sends with a pre-fade or post-fade option, but what does that mean?

It’s the Pick Off Point Again

As we discussed in the last episode (AFL/PFL), pre-fade and post-fade are really all about the pick off point. That is to say, at what point in the channel strip is the aux send being picked off. A pre-fade aux takes the signal before (pre) the fader. So, the level of the fader has no impact on the level of the aux send. A post-fade aux takes the signal after (post) the fader so the level of the fader does impact the level of the send. Sometimes, it’s really that simple. See, I told you these were going to be short posts.

Options, We Have Options

Back in the days of analog consoles, it was often possible to change the pick off point. I remember reading the manual of our old Soundcraft Series 2 in which it described breaking solder jumpers to move the pick off from pre-fade, post-EQ to pre-fade, pre-EQ. Sometimes, it could be done with jumper blocks on the board.

With the advent of digital consoles and DSP, it’s now easier than ever to change the pick off point. For example, Digico allows for pre-fade, pre-mute; pre-fade, post-mute; and post-fade, post-mute options. Pre-fade and pre-mute are both pre-processing while post-fade is after the processing block. Even the Behringer X32 allows for each aux of each channel to be set pre-EQ, post-EQ, pre-fade, post-fade. 

I especially appreciate the signal flow diagram showing your aux options. 

I especially appreciate the signal flow diagram showing your aux options. 

You’ll have to break out the manual to see what options your board has.

Why Use Them?

Generally speaking, we use pre-fade sends for monitors and post-fade sends for FX. Post-fade sends are also useful for things like broadcast mixes, and feeds to ancillary rooms. We want monitors to be pre-fade because we don’t want to be changing the musician’s mixes each time we make a house mix adjustment. If you’re getting complaints from musicians that their mixes keep changing, make sure you’re set to pre-fade auxes. 

For FX, we want the level going to the FX processor to be tracking with the dry signal going to the mix. If you sent pre-fade signals to an FX processor, even if you pulled the channel down, the FX would still be in the mix. Similarly, if you’re using a post-fade aux bus to mix broadcast, you want the fader changes of the mix to track to the broadcast mix. 

Adding to the Confusion

Some manufacturers make analog boards with a few pre-fade auxes and a one or two knobs labeled FX. The FX knobs are simply post-fade auxes that often feed an internal FX system. Typically, there is an output on the board to use an external processor with those FX sends, so don’t be limited to the internal FX (which may or may not be any good). 

Many analog boards will let you switch the send for each aux or a pair of auxes to pre or post. Again, be sure the switches are in the right spot if you want to keep your musicians happy.

Pre-fade and post-fade is one of those concepts that is really quite simple, but can cause a lot of problems if not implemented correctly. Hopefully, this post helps with that.

“Gear

Today's post is brought to you by DiGiCo. DiGiCo audio mixing consoles deliver solutions that provide extreme flexibility, are easy to use and have an expandable infrastructure, while still providing the best possible audio quality. Visit their website to learn more.

Today's post is brought to you by Pacific Coast Entertainment. Pacific Coast Entertainment is the premier event production company servicing Southern California and the western states. PCE offers a complete line of Lighting, Audio, Video, and Staging equipment for rentals, sales and installs. Where old fashion customer service meets high tech solutions. PCE, your one stop tech resource.