DAWs offer two ways to add effects to a mix: on a track as an insert or through an auxiliary channel called a return. This article focuses on return effects and the kinds of mistakes that can happen when you route sounds to a return effect using a send, starting with...
In my production days, I only used insert effects. I saw the return channels in my DAW and even noticed them being used in YouTube tutorials. But something just didn’t click. I imagine there are a few newbies reading this in the same situation—so keep reading!
The key benefit of return channels is that they can be used by multiple tracks at once. This makes them an ideal choice for the kinds of effects we use frequently in a mix, like reverb and delay.
For example, to achieve a natural, coherent image mixing jazz, many mixers will send guitars, vocals, and drums to the same room reverb. Unique spring reverbs and bouncing delays would only confuse the dimly-lit club atmosphere you’re trying to create. A good ol’ fashioned rock mix might follow the same approach, but opt for larger reverbs to evoke a stadium-sized space.
Even in an EDM mix where naturalism isn’t all that important, return channels are useful to streamline processing and save on CPU power. Imagine you have the same reverb plug-in on your clap, snare, and hi-hat; why not send them all to a single return instead, then blend the effect into taste? This way, you save the trouble of having to adjust each insert whenever you want to make a change.
For all this talk of return channels, it's worth mentioning there are several scenarios where an insert is a better choice. Here’s one:
Though we’ve told many cautionary tales on the iZotope blog about over-processing, treating sounds with a heavy hand can make them sound better—and certainly weirder. In these cases, where processing almost overshadows the sound itself, I find inserts work better. Want to manage a signal with distortion? Chop it with an auto-panner? Give it a chorusey eighties shimmer? Go for bold with an insert.
Return effects excel as a final sweetening stage for audio. Maybe a guitar needs a little air or depth, but you’ve already got a nice EQ setting on the track you don’t want to change. Finish it off by sending it to a return for modulation and reverb.
For more tips on when an insert will serve you better than a return (and vice-versa) I recommend this article by fellow iZotope writer, Nick Messitte: Aux vs. Inserts: to Send or Not to Send?
A submix is another use for an auxiliary track. If you have six guitar tracks and want to adjust the levels of all of them at once, group them together under a single aux track where this can be done. You can also solo or mute the group together this way.
The submix setup works a little differently in each DAW, but the end result is the same: the selected guitar track outputs are accessible from a single stereo channel. In large mixes where you need to make quick changes often, submixes are a necessity.
But there’s more! If your guitars need some kind of group processing, like a high-pass filter or some soft saturation, you can do this from the submix too. And if your guitars are getting in the way of your vocal, you can group the lead vocals into a submix and use them as a sidechain input for the guitars. Busy mixes where masking is a consistent issue often need this kind of control.
Because many DAWs hide return channels or tuck them off to the side, it's easy to forget that the send—which copies an audio source to the return channel—can be automated. With multiple tracks under a single dial, automating sends is a powerful mixing move. Don’t be afraid of automation while mixing, here is a guide to help.
For example: when the chorus kicks in, automate the lead vocal send higher on the reverb, then return it back to a lower, drier setting for the verse. At the same time, you might want to automate the pan dial on the reverb return to make the effect wider.
When an effect is used directly on a track as an insert, the dry/wet knob is a crucial parameter to manage. If the wet setting is too high, you will draw listeners’ attention to the effect and take away from the music. Too low and the effect won't have much effect at all.
Things work differently with return channels because the audio in a return channel is a duplicate of whatever is sent to it. Try it for yourself—send an audio source to a return channel without any effects. You will have two identical versions playing at full blast and a master bus in the red.
What does this mean for gain staging then? Depending on the effects you work with, best practices change. For time-based effects like reverb and delay, turn the wet control all the way up and use the send to control the blend between the original and processed version. Turning the wet dial down on the plug-in will only introduce more of the duplicated dry signal and overload the output channel. Dropping the return fader won’t do you any good either, since this will lower the effect level of everything that’s been routed into the channel. Bottom line: the send is your friend.
When you need to change the output level on compressors and analog-modeled plug-ins, refer to either the plug-in output or return fader. These effects are sensitive to input level changes, so changing the send level might disrupt the balance of the mix.
Though you will figure this one out quickly yourself, there is no need to stick to one effect per return channel. Adding a number of complementary plug-ins to the same return can create a unique atmospheric effect to blend tracks into.
You will also notice return tracks have their own sends, meaning you can feed the output of a return into another for further processing—or even feed it back into itself! This kind of routing can easily become complicated, so I recommended you take a moment to think about why you’re sending returns to each other before making any connections.
As a starting point, some mixers might send a vocal to a delay, then the send the output of the delay into a reverb. This way, the delay gets a longer, washed-out decay without muddying the vocal itself.
If you’re new to sends and return effects, I hope this article has given you a better idea of how to use them and what mistakes to avoid. Granted, there are other errors you can make, but what’s been provided here covers the most common ones.