YOU SEND ME

Aux sends are great for situations in which you want to send multiple mixer channels to the same effects processor, such as a reverb. When you use an aux send, route only a portion of the channel's dry signal to the outboard processor; that way, the dry signal will still show up on its channel fader, letting you control its level in the mix.

The dry signal does not noticeably decrease in level when you use an aux send. Rather, an amplified mult of the channel's signal is sent to the mixer's master aux send. From there the signal goes to your effects processor, along with the signals from other tracks using the same aux send.

The wet/dry mix on an effects processor is usually set to 100 percent when patched to an aux send, because the level of the wet signal is controlled by the mixer's effects-return faders or knobs. The dry-signal level, on the other hand, is controlled with its mixer-channel fader. That setup gives you independent control of wet and dry levels at the mixer.

The aux send's ability to apply the same effect to multiple tracks simultaneously has a couple of benefits. For example, fine-tuning the parameters of one effects processor that is used on a number of channels is more efficient than attempting to match settings on a number of processors that are dedicated to individual channels.

In addition, using aux sends for plug-in effects on a DAW lets you use CPU resources more efficiently than you could if you added effects to each track. Plug-in effects, especially reverbs, can be huge CPU hogs.

You'll quickly run out of CPU resources if you use the same plug-in (and redundant parameter settings) on inserts for multiple virtual mixer channels. A better way to add the same effect to multiple channels is to bus each channel to a common aux track and apply the plug-in just once to the aux track's insert, thereby applying the plug-in's effect to all bused channels simultaneously.

In Mark of the Unicorn's (MOTU's) Digital Performer, for example, you can use channel sends to route several background vocals to a common aux track by way of bus 1 (see Fig. 4).

Figure 4. You can lessen the strain on your DAW’s CPU by using an aux track to apply a plug-in to several tracks at once. Here, an aux track receiving input from bus 1 in Digital Performer receives effects-send signals from several tracks. The aux track then sends those combined signals to a Waves reverb plug-in by way of the aux track’s insert.

The aux track's input is set to bus 1 so it can receive all of the send signals and route their combined signals to a plug-in by way of its insert. Because you're using only one instance of the plug-in in this case, the drain on your CPU will be a fraction of what it would be if you instantiated the plug-in for each mixer channel.

ACT OF PRESERVATION

Many hardware mixers and some DAWs let you route an aux-send signal either pre- or postfader. When an aux send is configured postfader, the effect's wet/dry ratio is preserved at the mixer as you raise and lower channel faders; lowering a channel's fader simultaneously lowers the aux-send signal level. That keeps you from having to adjust effects-return fader levels at the mixer or wet/dry ratios at the effects processor every time you make a level adjustment with a track's channel fader. (In most cases, you'll want to keep the balance between a dry track and its effects relatively constant throughout the mixdown process.) As a result, postfader effect sends are used more often than prefader effect sends, although the latter configuration definitely has its uses.

As the name implies, a prefader aux send is not influenced by channel-fader moves, because the signal is sent to the processor through the aux send before it gets to the fader. Therefore, the processed signal level from a prefader aux send remains constant, no matter how you move its corresponding channel fader.

One use for this type of configuration is to keep a vocal track's reverb level constant while you lower its dry level. Set the level of reverb you want the vocal to have in the mix by turning up its prefader aux send, which is routed to your reverb unit, until the effect sounds right.

Then, slowly lower the vocal's mixer-channel fader. As you lower the fader, the vocal's dry level dips while the level of the processed signal remains constant. The result sounds as though the vocalist is walking away from you: the dry sound gets quieter, leaving just the reverberations of the room.

DOUBLE YOUR PLEASURE

A mono aux send works fine on lead vocals and other mono tracks but may not be exactly what you need to process a stereo pair of tracks that are routed to two mixer channels. Some mixers offer stereo sends for this purpose; other mixers, including many digital ones, let you pair two mono aux sends together so that they function as one stereo unit.

Usually the odd-numbered sends (for example, aux 1, 3, and 5) serve as the left channels, and the even-numbered sends (aux 2, 4, and 6) serve as the right.

You must have a stereo effects processor to take advantage of stereo or paired aux sends (unless you are employing the aux sends to feed a headphone amp, which is beyond this article's scope). Simply patch your mixer's left and right aux sends to the left and right inputs, respectively, of your stereo effects processor (see Fig. 5).

Figure 5. This is the correct way to route paired aux sends to a stereo effects processor and back to the mixer.

When using stereo or paired aux sends, how you pan the mixer channels determines which aux sends — left, right, or a combination of both — they will be routed to. For example, if the left side of a stereo keyboard track is panned completely to the left, its stereo aux-send signal will be sent only out of the left (odd-numbered) aux sends.

If you pan the keyboard channel dead center, it will be sent equally to both aux sends. Panning the two channels hard left and hard right, respectively, lets you keep the left- and right-channel effects processing discrete for each mixer channel.

GROUP STRATEGY

Discrete left and right processing offers a wider stereo field and avoids the phasing problems that occur when miked stereo tracks are combined into a mono aux send. Stereo aux sends can be used to process any stereo tracks, including acoustic guitar, background vocals, and drum tracks.

Background vocals and drums are often assigned to the stereo aux sends that serve mixer subgroups. Here's how you can use a subgroup's aux sends and inserts for more efficient and creative mixing.

Say you want to add the same reverb to three or more background-vocal tracks. You might be tempted to set the aux-send level that feeds your reverb unit for each mixer channel separately. However, as the mix progresses and you begin to finesse the aux-send level for one of the channels, you'll likely need to rebalance the aux-send levels for all of the other background-vocal channels, as well. Fortunately, there's a more efficient way to do that.

You can work faster by busing all of the background-vocal channels to a common subgroup. To spread out the background vocals in the stereo field, bus their channels to two subgroup faders, pan the channels so that each one is where you want it to appear in the stereo field, and then hard-pan one subgroup channel fully left and the other fully right. Now you can use a single subgroup aux send to adjust the amount of reverb (or other effect) for all of the background vocals routed to that subgroup.

That strategy is beneficial only if you want to add the same amount of effect to all of the tracks in the subgroup, as is often the case. Subgrouping the background vocals also lets you control the levels for the background-vocal tracks using only one (in a mono subgrouping) or two (for stereo subgrouping) faders.

Some high-end mixers (Harrison consoles, for example) also offer subgroup inserts. They let you simultaneously and equally process subgrouped channels through outboard dynamics processors or equalizers.

Many top-flight engineers will bus an entire drum kit into a stereo subgroup (or, alternatively, to a pair of multitrack bus outputs), out to a stereo compressor, and then return the compressed drums to a pair of line inputs on the console. That setup controls the drum kit's level as a whole while enhancing mic bleed to give the kit more of a live sound.

When you bus a DAW's virtual mixer channels to an aux channel, you are actually subgrouping. As noted previously, subgrouping a DAW's virtual mixer channels onto an aux channel enables you to conserve CPU resources by using only one instantiation of a plug-in effect for all of the subgrouped tracks.

It may surprise you to know that even the most inexpensive mixer offers subgrouping of sorts, though you might not think of it as such. The king of all subgroups is the stereo master bus, whose level is controlled by your master fader.