Insert Effects, Aux Inputs, and Buses
Mixers provide several different paths for the audio to take. To fully understand what a mixer is capable of, you'll want to know about insert effects, auxiliary inputs, and buses. Understating these concepts will make you comfortable on any mixing board, regardless of the brand.
An insert effect is an effect that can be plugged into one, and only one, channel. You do this via the insert jack on your mixer, which sports a tip ring sleeve (TRS) connector made for insert effects. Insert effects are typically used only for compression and EQ because you cannot mix how much of the signal gets the effect—it's all or nothing. Because compression and EQ work fine in these cases, insert effects are perfect for this. Effects are covered in detail in Chapters 15 and 16.
Aux inputs are used for effects that require a blend of effected and noneffected signals. Effects like reverb, chorus, and delay sound terrible when you hear only 100 percent effects. Aux effects are also used when you wish to use the same effect on more than one channel. An aux input is plugged into the master section aux input/output, and each channel has a control for how much of the effected signal to blend in with the dry, unaffected signal. This is great when you have hardware effects processors and you have to make the most out of a few pieces of gear. On the computer side, aux effects do the same as their hardware counterparts. You can usually have as many aux effects as you want in software, because you can reuse the same plug-in on multiple tracks.
Buses act like a sub-master fader. That is, you can send a bunch of channels to a bus, and the bus fader will raise or lower as one, all of the signals fed into it. For example, let's say you're mixing a drum kit. You have four channels of drum sounds and you have the perfect mix between the individual drums. By itself, the drums sound great, but when you add in other instruments, you notice the drums’ volumes are a little low. You could raise each drum track one by one, but that means that you lose that perfect balance you worked so hard to get.
If your outboard mixer or virtual mixer supports buses, you can assign all the drum tracks to bus one, which sends all four signals to one volume control (the bus). Then when you turn the bus up, all four signals fed into the bus get louder while retaining their individual balances. You can get multiple buses with the better outbound mixers. The more you spend, the more buses you get. All the major computer recording software supports buses. It's a great tool for recording, and it is commonly used to balance groups of instruments like drums and double-miked instruments.
Buses are also used when connecting to less capable audio interfaces. Many consumer audio interfaces allow only eight or fewer inputs total, so buses comes in handy if you need to consolidate four drum microphones to one or two channels, again regaining control of the final mix, not just the individual channels.