Via the channels, the signal is picked up, manipulated and sent to the destinations we will shortly take a look at. In actual fact, every one of the mixer's channels contains two channels, but for the moment let's pretend there is only one, and concentrate on this single channel only.
A channel can receive both a line input and a balanced microphone input [Balanced Electric Connections ] . The main difference between these two signals consists in the fact that a microphone signal has a far lower tension than a line signal [12 ] , and therefore the two inputs are amplified differently (for a more detailed explanation of this topic, go to the Amplification section [Amplification ] ).
Let's take a look at the various stages of a channel:
Gain:
Both inputs, the line input and the microphone input, have a gain potentiometer which regulates the signal's amplification-level; often it is the same potentiometer that controls the two gain-circuits. Through a switch we'd then select the kind of input (microphone or line).
Gain
PAD (attenuation): allows input-signals that are too high to be decreased by 20-30 dB.
Phase-inverter: from this stage onwards the channel becomes a single channel. This stage literally inverts the phase (exchanges the negative pole with the positive pole).
Equalizer: Parametric Equalizer. For a detailed description go to the pertaining section [Parametric equalizers ] .
Parametric Equalizer
Filter: Supplies the channel with a high pass filter [Filters ] which makes sure low frequencies are effectively removed.
Filter
Insert Socket: this socket is in actual fact located in the posterior connections of the mixer, not on the channel itself. We have access to this socket via the patchbay [PatchBay ] which shall be described in one of the following sections. It consists in two sockets through which one can insert one or more effects in a series, as shown in the following diagram:
Insert Socket
By inserting a connector into the insert-out socket, the direct insert-out/insert-in connection is interrupted and the signal is sent through the external modules.
- These are potentiometers that pick up a copy of the channel's signal and send to an apposite bus [13 ]. To better comprehend the way aux send works, we will refer to the following diagram:
Auxiliary send
Example of aux send
In our example we have imagined 4 aux send potentiometers for each channel, two pre-faders and two post-faders. This means that the copy of the signal that is picked up by an aux send pre-fader is independent from the channel's main fader, whereas the one picked up by the post-fader isn't. In a moment we will see when one type of aux send is needed rather than another. So- through aux sends we can create a series of auxiliary mixes whose overall level is controlled by its respective aux send masters (that are located in another section of the mixer and which we will investigate later [Aux send master ] ). For the moment this will suffice. Next we will take a detailed look at the usage of aux send in various situations.
Routing matrix: Its function is to route the signal towards the groups (group bus - they are located in another section of the mixer and we'll be looking at them shortly [Mixer: groups ] ) or towards the stereo bus L-R [Master fader ] . If our mixer were to have 8 groups, through the routing matrix we could route the signal to any group couple and also to the mix bus (in our practical case: 1-2, 3-4, 5-6, 7-8, L-R).
Routing matrix
Mute: By pressing this button, the channel is interrupted. There are various situations in which this is necessary (for example, imagine that during mixing you wanted to listen to the recorded piece without vocals, in this case all you'd have to do is press the mute button on the vocal channel, rather than having to turn the fader down manually, thereby also losing its original position).
Mute
Solo: By pressing this button all the other channels are put in mute mode (imagining, for example, that we only wanted to hear the voice this time, if we press the solo button on the vocal channel, all the other channels would thereby be muted).
Solo
Fader: It controls the signal that is routed to the mix bus or to the groups. In the following diagram we can distinguish the signal-routing buttons that route the signal towards the groups or towards the mix-bus.
Fader
Panpot (panoramic potentiometer): Controls the percentage of the signal sent to the a bus couple. If, for example, the panoramic control is rotated entirely in a clock-wise direction and the routing matrix sends the signal to the group-couple 7-8, we'd route the channel's signal towards bus 8. If, on the other hand, the pan is rotated entirely anti-clock-wise, the signal will be sent to bus 7. With the panoramic control in a central position, the signal will be equally distributed to bus 7 and 8.
Panpot
Monitor fader: In the recording studio, signals are recorded, therefore it is important to have the possibility to separate the recording levels from the listening ones. This is the reason why a studio mixer in actual fact has two channels within each single channel strip.
The second channel, called monitor path, and which is located underneath the main channel, serves the purpose of feeding the so-called monitor bus. For the moment it will suffice to know that on each channel there is another fader, which is usually smaller than the main one, and which routes the signal towards a bus which is different to both the groups, and the mix bus, and which is called monitor bus.
Monitor fader
OEvery fader of the monitor kind, is always accompanied by its respective panoramic potentiometer which controls the percentage of signal picked up at the channel-input to be sent to the Left and Right channels of the monitor bus.
We will call the channel that passes through the larger fader main channel and the one we've just described monitor channel reason for the presence of two channels in one, is that a mixer can undertake two status: the recording status and the mixing status. By the terms used to describe these two roles we can deduce their separate functions. What is important however, is that depending on the role the mixer is fulfilling in a certain moment, the main channel and the monitor channel are fed by different signals and thus have different functions. We will see this in greater detail further on, when we will describe in detail the recording and mixing phases.
[12 ] the input lines are uses with signals coming from preamplified circuits. In other words, the line signals have already gone through its preamplfication stage and therefore have a higher voltage. Another difference concerns impedance adaptation, which is explained in its pertaining section [Amplification: DI Box ]
[13 ] A bus is a channel in which a series of signals are made to converge. The mixer's most important bus is the output stereo bus, from which the signal that has resulted from the mixing of the signals present on the channels, is picked up. Other buses include group buses, solo buses and monitor buses, which will all be described in the next chapter.
Related topics on Wikipedia
Diagram of a mixer's channel