The Anatomy of a Mixer

Considering the amount of messages at the message boards about busses, send/receive loops, main and monitor outs and all the other knobs, jacks and faders on the surface of a mixing console (also called a board, I may use those terms interchangably), I figured it is about time to try to cover the topic in a column. All of these components and signal routing features can help you greatly in your recording efforts, but only if you know what they do and how they work. What I will cover here is the different signal routing options and some examples about when each is useful or even neccessary. This column assumes you already know what the level fader(or knob in rare cases), the gain knob (sometimes called Trim) and the EQ settings are and how to use them.

We take a look at each section of a channel panel from the top down on this example from a Mackie mixering console...keep in mind that not all mixers have all these sections in the same order, but they are usually called by the same (or similar) names.

Gain (or Trim)

At the top we have the gain (on Mackie called the Trim), which, as I stated above, we we won't get into deeply, because, well, there's not much to it, it's just a volume knob...

Aux Send/Return Loops

This is the route by which you can send the channels signal out of the board not to return until it hits the master section to be mixed back into the main signal. The send knob controls the percentage of the signal which is leaving the board. These loops also come in pre and post loops, and many boards make them switchable so any loop can be pre or post. What this means is that the signal is sent out of the channel path before (pre) or after (post) the preamp section of the channel.

You may notice on this board that two of the sends act as loops 3, 4, 5 and 6. These are switchable, there is a button there that you press to tell the board whether you want one knob to set the level of send 3 or 5 and the other send 4 or 6. Kind of a cool feature for having more loops without using more surface space. Some consoles have a button you press to make the knob control one channel and release the button to control the other, other manufacturers make push-and-pull knob, which I personally prefer, that you pull up to control one send and push it down to control the other.

The board that I am using to the left has no monitor sends in the channel panel, but many do. These monitor sends are just paths out of the board, no return, they make it possible for you to send a different mix to a set of monitors (like headphones, for example) so someone recording their part can have the mix set to the levels that help them perform the best. Some people like to have the part their playing cranked up, or the part of an instrument they have to sync with, these sends make it possible to give them that mix without changing the mix in the control room or going to the recorder.

EQ

The EQ section, as stated, we will also not dig into because most people know what it is for and how it works...the one thing I would like to point out is that on this board (and many others) is that the EQ frequencies are "sweepable". This means that you not only have a mid EQ setting, but you can actually define exactly what the middle of the mid's frequency is, kinda like a parametric EQ. Some people refer to this type of EQ a "paragraphic" EQ, which to me seems silly, but it does get the point across. Many boards also have high or low pass filters that do just what they say...they filter out the high or low frequencies if you need to get rid of rumble or feedback squeels...

Panning

This is obvious, it sets your location in the stereo field from left to right.

Mute and Solo Buttons

These buttons do just what they say...Solo mutes every other channel on the board so you can isolate any instrument for fine tuning the sound. Mute just turns off that channel if it getting in the way of fine tuning another.

Main Fader and Subgroup Busses

The main fader is the main level setting of the board, it should usually be set at the 0dB level and any radical volume adjustments should be done with the Gain/Trim knob. These faders are really nice for doing fade outs tho, cuz they are big and easy to deal with.

Beside the fader you see the Subgroup buttons. These control which busses the signal comes out of. This channel panel example came from a 32 channel / 8 bus board. This means there are 4 stereo pairs of paths out of the board. You just press the buttons of the busses you want the signal to go out of. These are useful for setting up different monitor subgroups, or grouping by instrument. For example sending every channels from the drum kit to one subgroup to get it to a stereo output, or if you are miking a horn section you can send them all to one subgroup. Many subgroup section actually have their own aux loops as well which means if you send all the drums to one subgroup, you can add reverb to the whole kit at once with this subgroup. Just rememeber, you can send each channel to as many subgroups as you want or need to. This my sound silly, but you can lay pretty good odds that somewhere down the line you will figure out a use for these and wonder how you ever got by without them.

Beyond the Channels

OK, now we move a bit beyond the picture at the left. All the signal routing done at the channel level goes to the "Master Section", pictured at the right. Not every console has these features, some have more, but I though this one had the common ones. Most consoles use the same names for everything, but not in the same order. This picture is not from the same console as the channel strip above is.

First we have the controls that allow you to path some "wet" signal to the monitor mixes, if you have them, to allow anything that is passed to the monitors to have some of the effects. Sometimes there are also controls here to set the level of the return signal of an aux send, but this is usually controlled by the processor itself. There is usually also controls to set which group you want the aux sends sent to.

Then there is also usually some sort of control for any tape input you mixer may have and knobs or button to control where it comes out, meaning the mains, monitors, or any other output from the mixer.

Then there comes the faders that control the volume of each group of outs, usually some sort of LED lights and clip indicators, plus sometimes some button to switch back and forth between which outs are being shown in the LED's if there is not an LED built in for each group. These faders control the volume that leaves the board to head for the amplifiers, recorders, or where ever you route it. They are generally marked as "main" outs, "sub" outs, sometimes there is a "control room" out, or they are numbered in pairs. Where they are numbered in pairs, they are stereo linked. However, you can use them seperately with clever use of panning. But, on boards where the stereo mix is controlled by only one fader, then that makes it harder.

In Conclusion

With som oney different models and features of mixing consoles. It is would be impracticle to cover it all here. I do believe, however, that this column gives you the basics of signal flow and process of the average mixing board.

Above what I have covered here, there are also automated boards, in which you can "save" settings to memory, program fade-outs and such and it will do it by itself, some have monitors like a PC for a user interface. The list goes on...But, I hope you got something out of this that you can take back to your studio and get a little better sound, or at least knowledge of how it is travelling through your mixing console.