The Parallel Universe of Send Effects

Send effects are good for so much more than reverb

by Craig Anderton

There are four main ways to add effects with digital audio workstation recording software. The most common method is to add software plug-ins as series insert effects—the track’s audio goes through the effect, then into the DAW’s mixer. Some DAWs also let you use spare audio interface I/O to route a track through external hardware effects.

There are also master effects, which affect all buses and all tracks for an entire mix. However, one of the most useful options is adding effects to a send (or auxiliary) bus as this lets multiple tracks feed a single effect, and simplifies techniques like parallel processing.

HOW SEND EFFECTS WORK

Audio tracks use send controls to “pick off” some of the track’s audio and send it to a bus. An effect inserted in that bus processes any audio it receives. The classic send effect application is reverb, where different tracks send different amounts of audio to the send reverb effect—for example, if you want lots of reverb on voice and guitar but not bass, you’d turn up the voice and guitar track send controls that feed the reverb bus, while leaving the bass’s send control down. The send bus output re-enters the DAW’s mixer via a “return” channel or track (Fig. 1).

Figure 1: This Ableton Live project has two returns for send effects—Delay and Reverb. The Guitar, Vocal, and Drums tracks all send some signal to the Reverb, but only the Guitar track sends audio to the Delay. The Delay bus is selected to show its two send effects: A Line 6 POD Farm stereo delay, preceded by EQ that reduces low and high frequencies in order to accent the delay’s midrange.

Sends typically can be pre- or post-fader. With post-fader selected, reducing the track’s main fader simultaneously reduces the send level. With pre-fader, only the send level control determines the send level, independently of the track fader’s setting. Furthermore, Mute and Solo buttons typically affect a send only if it’s post-fader.

KEEP IT WET

When using send effects that have a wet/dry balance controls (like reverb or delay), remember that this effect is in parallel with the track feeding it. As the original track is feeding the DAW’s mixer with a dry signal, you’ll usually set the send effect for wet sound only, then use the return track’s level control to balance the amount of wet signal with the original track’s dry signal.

Another trick involves changing phase. If you reverse the phase (polarity) feeding the send bus, this will tend to cancel out any residual dry signal in the send bus effect. For example if you’re using a phaser as a send effect, there’s still some dry signal in there even if the phaser’s wet/dry control is set to all wet. Canceling out some of the remaining dry signal produces a kind of “super-phaser” effect.

SENDS AND SIDECHAINS

Sidechaining with software plug-ins also makes good use of sends, because a track send usually provides the track’s signal to a sidechainable device. Typically, the sidechain input will show up as an available send destination (Fig. 2).

Fig. 2: In Cakewalk Sonar, a send from the drums feeds a control signal to an Expander/Gate processor inserted in the bass track. There’s also a Compressor on the bass track; this is being gated by the Damage drums in Kontakt.

Note that for sidechaining, you’ll almost always want the sidechain set for pre-fader, so that the amount of signal feeding the sidechain is constant. This also lets you solo the sound of the track with the sidechained effect without muting the track that provides the sidechain signal.

Also remember that when sidechaining via a send bus, you can insert additional effects to process the control signal. For example with a dance mix, you might want to filter out everything but the snare so you can “pimp” a compressor on another track whenever the snare hits.

SENDS AND PARALLEL EFFECTS

• Sends are an easy way to create parallel effects, so any parallel effects applications work well. Here are a few examples.
• Use a send effect to parallel a wah or envelope-controlled filter with the track it’s processing. This prevents “thinning out” the main track.
• With bass, keep the full, round bass sound in the main track, and send some audio to processors like distortion, chorus, wah, etc. Parallel processing keeps the low end intact.
• Send effects can help provide stereo imaging. Use two send effects with short delays (like 13ms and 17ms), then pan one send right and the other left. This adds width and ambience. Then, these two sends could feed another send that feeds reverb, thus adding a room or hall sound.
• If you have a chain of hardware effects, most DAWs have “external effect” plug-ins that can feed a track or send’s audio to an interface output. This patches to the hardware effects, whose output returns to a spare audio interface input. Although this is usually implemented as an insert effect, it works just as well for sends. The only caution is that this introduces additional latency; you may not notice this with reverb, but the more robust your DAW’s path delay compensation, the better. The latency may be enough to cause problems while tracking, but won’t be an issue during mixdown.
• Send effects make it easy to maintain consistency with doubled parts. Rather than trying to set up insert effects identically for each part, simply create one send effect, and send audio from each doubled part to the send bus.
• Sends are great for multiband processing, because you can send particular frequency ranges from a track to different sends, and process those bands separately. To divide a track into different frequency bands, one option is to use a multiband compressor as a crossover (assuming you can solo individual compressor frequency bands, and set the compression ratio to 1:1 so there’s no compression). Insert the multiband compressor as an effect into each send, and use the same frequency ranges for each one. Then, solo individual bands to process only those frequencies for a given send.
• Amp sims can often add a delightfully trashy sounds to drums, along with some ambience. However, a little goes a long way—put the amp sim in a send efefct so you can dial in a subtle amount in parallel with the drums.

Those are enough ideas to get you started, but be creative and you’ll surely come up with some more. And if you do, feel free to add a comment and tell the world about it!

  Craig Anderton is Editor Emeritus of Harmony Central. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.