The Unique Geek

The Unique Geek
December 21, 2010

Auxes, Busses and Sends, Oh my!

In another lifetime I was doing tech support for a company that made hardware interfaces for recording software. I quickly learned on the job that I wasn’t really tech supporting our products, but rather I was explaining the Windows OS a lot or some other company’s DAW.

Plugging Cables into Sound Mixer

It was in the conversations with folks on how to get their DAW to point to our drivers that the folks would take advantage of the situation. “Hey, man while I got you here”, they’d start. And, this is never a comforting lead-in for a tech support person, by the way.  A couple of these conversations led to, “can you tell me what an aux is and what a send is?” It made me pause in my tracks and realize that if you’ve never sat in front of a mixer and dealt with the hardware world – how would you know what to make of these things in the software world?

Don’t get me wrong. I had the hardest time with the concept of “send/return” on my first mixer. The first band I was in had a very patient musician (friend) that tried to get this into my thick head for some time.  I understand how hard the concepts of inserts, sends, busses and auxes can be. Let’s dumb them down to their simplest meanings. This is really made necessary by my limited capacities. So, humor me.

Effect Families

Before we move on to the boring (errr riveting) topics at hand let’s talk about “effect families” so that we’re all on the same page. More times than not, effects fit into 1 of 3 families: gain-oriented, time-oriented and modulation-oriented effects. Gain effects are those that can add gain such as filters, eq, compression, limiting, distortions, tape emulations and some that come with the clever name of “gain.” Time effects are those that play with time such as delays and reverbs. Modulation effects are the fun ones like chorus, phaser, tremolo, rotary and flanger. But, seriously, who uses flangers anyway?!?! I mean, in the last twenty years, who uses it? There are pitch-oriented effects, utility effects, but for our purposes – let’s stick to these three families. And, let’s never speak of flangers again.



An insert is something that you (wait for it) insert into your signal path. All of audio is about a “signal path” – where is that sound going to or coming from?


If you think of audio as water, most times, it’s makes it easier in your mind to think through. All of what we are discussing is plumbing. Inserts are interesting because it gives you the ability to effect 100% of the audio on a channel with something. Since it is going to effect 100% of the signal (let’s say this is a vocal track) we should be careful about what kind of effects are on inserts. 9 times out of 10 – this is a gain-oriented device or effect. Why? Because what is the use of 50% of the vocal being compressed or de-essed? What is the use of eqing 25% of the vocal? You intend to eq the vocal – so 100% it is. Same goes for you auto-tuners out there – insert it.


Busses and Auxes are similar. But, we use the term “bus” a few different ways in recording. All in all though, when we bus, you can just think of it as the name implies. We put some sound on the bus and send it off. Bussing, in recording world, can mean routing (like a bus route) or, often, it means to sum together several sources into one spot. This is where the aux comes in.An aux is an auxiliary channel ( an extra channel) on the mixer that a bunch of channels can be bussed to. So, you can bus your sound to the aux channel.

Side note A: “Bus” is a verb and a noun. You can bus (divert) audio to a bus (auxiliary channel). I like to “bus to an aux” so that my little, little mind can keep track of these concepts.


Side note B: to clear your head on “tracks” and “channels” think of that reel to reel machine and a real mixer. Tracks are on the tape (or hard drive) and channels are on the mixer.



Often times when someone talks about a bus, they mean a sub group of channels that gets combined so you have one fader that control all of them. This makes it easier in your head to keep track of everything. Let’s say we have 10 channels of drums, 4 guitar channels, 4 of vocals and 3 of synths. To make everything easier, you could make bus/aux 1 for drums, bus/aux 2 for guitars, bus/aux 3 for vocals and bus/aux 4 for synths. Now, we are down to just 4 faders controlling the mix after you’ve got every channel about where you want them in your mix. Plus, we can use just one eq and compressor for all of our drums. We’d insert an eq and compressor on bus 2. In your DAW, you make sure you have 4 busses or aux channels (depending on what your DAW calls them) and set your individual channel outputs to the appropriate bus. After you’ve done your 21 channels of tweaking, you can then get down to thinking of them as four groups of sounds and not constantly bounce around amongst 21 individual channels. Then you are down to, “hey, the drums need to be louder than the guitars”, and this makes life easier.


Sends are cool. Sends were the ones in school that got good grades and, yet, instigated a shaving cream fight. With sends, you can divert off some of your signal to go do something else.



So, in plumbing terms you’ve just created a y-joint, but with valves to control how much gets sent away from the main pipe. This is where we get time and modulation effects involved. We are going to put a reverb, say, on an aux channel. We insert the reverb on an aux channel, say, to sit and wait for someone to get bussed over. Make sense? So, on my vocal track that needs a little fairy dusting, I tell my send that it is going on “Bus 6.” Then, with the send knob I choose how much of this channel I wish to bleed over to where that reverb is sitting. The input on this Aux channel that I labeled “reverb” is going to be set to “Bus 6.”

Send Amount

This is the beauty of the send – we “send” some of the audio over on a bus to an aux channel. Why some? Because, again, this is a time when you may mean to only put 25% of the vocal track into a reverb and not 100% of it. This is how we retain a present vocal sound and still have it sound like it is in a cathedral at the same time. Secrets of the pros, my friends; secrets of the pros.

This is also how we squeeze more out of our CPU. Any time I want to use some reverb I simply tell a send on any channel to go out on Bus 6 and I get to share one reverb amongst several tracks. If you inserted a reverb on 12 channels that needed some reverb, you’ll hit the wall faster than if 12 channels shared that same reverb.

Side note C: I’m not going to bother with what “returns” are as we are only dealing with DAWs here and not analog mixers.

Quick review:

  1. We insert an effect on our channel or aux channel.
  2. We bus some audio (with a send) to an aux if we want to effect our channel.
  3. OR – we bus 100% of a channel’s output (no “send”) to an aux to act as a fader for a group of channels.
  4. On individual channels, time and modulation tracks are usually “sent” to and gain effects are inserted.

Output to Busses

Channels, Auxes and Master Channels

Now the only thing to keep track of (to keep yourself out of trouble) is to think about where everything is going. Not, “well, in this economy and given the government’s inability to react quickly to market forces”, type of ‘where we are going’. I mean you need to think about where your audio is coming from and going to. Again, all of this is plumbing. It’s easy to see how this is plumbing when you connect cables on your stereo system (do people still have those?) where you do “audio out” to “audio in.” Rather, in a DAW, you need to pay attention to each channel’s in and out part of the channel strip.

If you need to set up a group or bus like we do with 10 channels of drums (from hats, toms, overheads, etc) then you set each of these outputs to the same bus (call it Bus 2). Ah! But, make sure to go over to that aux channel and set it’s input to that same bus – Bus 2.

What you’ve done when you told the output of your hi-hat channel to be Bus 2 is that it is no longer going right to the master output. So how does it get to the master output, you ask? Why, Bus 2’s output is….(drum roll please)…Master Out, 1-2 (whatever your DAW calls it).

If you pay attention to what the input is on your channel, you’ll hear sound coming into that channel. If you mind where that output for the channel is going, you’ll know if it went to an aux channel or the master channel. If you need to get your guitar sound into some reverb, go tell that send where it is going.

If your head is still spinning, I am sorry. The way all of this is made easiest to understand is if you were forced at gunpoint to hook this stuff up in an analog setting. This is where you’d actually see the cables (pipes in our metaphor) taking sounds in and out – to and fro. But, I’ll tell you; it’s only at gunpoint that I would ever go back to that world.


  1. [...] At first we are concerned with getting everything under control. When you are first given a song to mix you are looking at a problem and you are its solution. What is that problem? Well, for one, you should be staring off with each channel’s fader at 0 dB. First thing I do is to sort everything out. “Okay, where are my percussion tracks”, I ask. Then it’s finding the bass parts and so on. You have the channels not at infinity, but 0 because you are going to have to solo channels to figure out what’s what. Sometimes you get songs and a track is called “Okra Troll” and you realize it is actually someone playing tambourine. Remember, this is musicians we are talking about. So, it’s time to put all of the instrument families together and start giving these groups their own colors in terms of faders. Then, if you are like me, you buss similar groups of instruments together. All of the percussion instruments may get bussed to an aux channel I call, “drums” (clever, I know). [See previous blog about auxes and bussing.] [...]