Editing Mixing console (section)

==Structure==
[[File:Yamaha MC2403 audio mixing console (1992).jpg|right|thumb|Yamaha 2403 audio mixing console in a 'live' mixing application]]
{{multiple image |align=right |direction=horizontal
|image1=Mackie ONYX 80 strip.png     |width1=64
|image2=Mackie Onyx 80 group bus.png |width2=60
|image3=Mackie ONYX 80 master.png    |width3=108
|footer=Channel input strip, Group, and Master section on Mackie ONYX 80
}}

An analog mixing board is divided into functional sections. Some of the more important functional sections are subdivided into subsections.

===Channel input strip===
The channel input strips are usually a bank of identical [[monaural]] or [[stereo]] input channels arranged in columns. Typically, each channel's column contains a number of rotary [[potentiometer]] knobs, buttons, and [[fader (audio engineering)|fader]]s for controlling the [[gain (electronics)|gain]] of the input [[preamplifier]], adjusting the [[Equalization (audio)|equalization]] of the signal on each channel, controlling routing of the input signal to other functional sections, and adjusting the channel's contribution to the overall mix being produced.

The types of inputs that can be plugged into a mixer depend on the intended purpose of the mixer. A mixer intended for a live venue or a recording studio typically has a range of input jacks, such as [[XLR connector]]s for microphones and the outputs from [[DI box]]es, and [[1/4" jack]]s for [[line level]] sources. A [[DJ mixer]] typically has [[RCA connector]] inputs for pre-recorded music being played back on [[turntable]]s or [[CD player]]s, and a single mic input.

Depending on the mixer, a channel may have buttons that enable the audio engineer to reroute the signal to a different output for monitoring purposes, turn on an [[attenuator pad]] (often reducing the signal by 15 or 20&nbsp;dB to prevent [[audio clipping]]), or activate other features, such as a [[high-pass filter]]. Some higher-priced mixers have a [[parametric equalizer]] or a semi-parametric equalizer for one or more of the equalizer frequency bands, often the [[Mid-range speaker|middle range]].

The channel strips are typically numbered so that the audio engineer can identify the different channels. For each channel input, a mixer provides one or more input jacks. On consoles for mid- to large-sized live venues, and sound recording consoles, these input jacks are numbered and consolidated in a [[patch bay]]. On smaller mixers, the input jacks may be mounted on the top panel of the mixer to facilitate the connection and disconnection of inputs during the use of the mixer.

The input strip is usually separated into sections:
* [[Jack (connector)|Input jack]]s
* [[Microphone preamplifier]]s
* [[Equalization (audio)|Equalization]]
* Dynamics processing (e.g. [[dynamic range compression]], [[Noise gate|gating]]), if supported
* Routing, including direct outs, [[auxiliary-send]]s, [[Panning (audio)|panning control]], and subgroup assignments
* Level-control [[Fade (audio engineering)#Fader|faders]] (on small mixers, these may be rotary knobs to save space and cost)

On many consoles, these sections are color-coded for quick identification by the operator. Each signal (e.g., a singer's vocal mic, the signal from an electric bass amp's [[DI box]], etc.) that is plugged into the mixer has its own ''channel''. Depending on the specific mixer, each channel is stereo or monaural. On most mixers, each channel has an [[XLR connector|XLR]] input, and many have [[RCA connector|RCA]] or quarter-inch [[TRS phone connector]] line inputs. The smallest, least expensive mixers may only have one XLR input with the other inputs being line inputs. These can be used by a singer-guitarist or other small acts.

====Basic input controls====
The first knob at the top of an input strip is typically a ''trim'' or ''[[Gain (electronics)|gain]]'' control.  The input/preamp conditions the signal from the external device and this controls the amount of amplification or [[attenuation]] that is applied to the input signal to bring it to a [[nominal level]] for processing. Due to the high gains involved (around +50 [[decibel|dB]], for a microphone), this stage is where most noise and interference is picked up.  [[Balanced]] inputs and connectors, such as XLR or phone connectors that have been specifically wired as balanced lines, reduce interference problems.

A microphone plugged directly into a [[power amplifier]] would not produce an adequate signal level to drive loudspeakers, because the microphone's signal is too weak; the microphone signal needs a [[preamplifier]] to strengthen the signal so that it is strong enough for the power amplifier. For some very strong [[line level]] signals, the signal that is plugged into the mixer may be too strong, and cause [[audio clipping]]. For signals that are too strong, a 15&nbsp;dB or 20&nbsp;dB [[Attenuator (electronics)|pad]] can be used to attenuate the signal. Both preamplifiers and pads, and the controls associated with them, are available in the input section of most mixing consoles.

Audio engineers typically aim at achieving a good ''gain structure'' for each channel. To obtain a good gain structure, engineers usually raise the gain as high as they can before [[audio clipping]] results; this helps to provide the best [[signal-to-noise ratio]].

A mixing console may provide [[Insert (effects processing)|insert]] points after the input gain stage. These provide send and return connections for external processors that only affect an individual channel's signal. Effects that operate on multiple channels connect to auxiliary sends (below).

====Auxiliary send routing====
The ''auxiliary send'' routes a split of the incoming signal to an auxiliary bus, which can then be routed to external devices. ''Auxiliary sends'' can either be pre-fader or post-fader, in that the level of a pre-fader send is set by the ''auxiliary send'' control, whereas post-fade sends depend on the position of the channel fader as well. ''Auxiliary sends'' can send the signal to an external processor such as a reverb, with the return signal routed through another channel or designated auxiliary return. Post-fader sends are normally used in this case. Pre-fade ''auxiliary sends'' can provide a monitor mix to musicians on stage (which they hear through [[Foldback (sound engineering)|monitor speakers]] pointing at the performers or in-ear monitors); this mix is thus independent of the main mix produced by the faders.

[[File:School - Board 2.jpg|thumb|left|upright|Program channels on a radio soundboard]]
Most live radio broadcasting soundboards send audio through ''program'' channels. Most boards have 3-4 program channels, though some have more options.  When a given channel button is selected, the audio will be sent to that device or transmitter.  Program 1 is typically the on-air live feed, or what those listening to the broadcast will hear.  Other program channels may feed one or more computers used for editing or sound playback.  Another program channel may be used to send audio to the talent's headset if they are broadcasting from a remote area.

===Channel equalization===
Further channel controls affect the equalization of the signal by separately attenuating or boosting a range of [[frequencies]]. The smallest, least expensive mixers may only have bass and treble controls. Most mid-range and higher-priced mixers have bass, midrange, and treble, or even additional mid-range controls (e.g., low-mid and high-mid).  Many high-end mixing consoles have [[parametric equalization]] on each channel. Some mixers have a general equalization control (either [[Graphic equalizer|graphic]] or parametric) at the output, for controlling the tone of the overall mix.

====Cue system====
The [[cue (audio)|cue system]] allows the operator to listen to one or more selected signals without affecting the console's main outputs. A sound engineer can use the cue feature to, for instance, get a sound recording they wish to play soon cued up to the start point of a song, without the listeners hearing these actions. The signal from the cue system is fed to the console's [[headphone amp]] and may also be available as a line-level output that is intended to drive a monitor speaker system. The terms AFL (after-fader listen) and PFL (pre-fader listen) are used to describe respectively whether or not the level of the cue signal for an input is controlled by the corresponding fader. Consoles with a cue feature have a dedicated button on each channel, typically labeled ''Cue'', ''AFL'', ''PFL'', ''Solo'', or ''Listen''. When cue is enabled on multiple channels, a mix of these signals is heard through the cue system.

Solo in place (SIP) is a related feature on advanced consoles. It typically is controlled by the cue button, but unlike cue, SIP affects the output mix; It mutes everything except the channel or channels being soloed. SIP is useful for setup of a mixing board and troubleshooting, in that it allows the operator to quickly mute everything but the signal being adjusted. For example, if an audio engineer is having problems with clipping on an input, they may use SIP to solely hear that channel, so that the problem can be diagnosed and addressed. SIP is potentially disastrous if engaged accidentally during a performance, as it will mute all the channels except one, so most consoles require the operator to take very deliberate actions to engage SIP.

====Busses and submix====
Each channel on a mixer has a volume control (''[[Fader (audio engineering)|fader]]'') that allows adjustment of the level of that channel. These are usually sliders near the front of the mixing board, although some smaller mixers use rotary controls to save space. The signals are summed to create the main ''mix'', or combined on a ''[[Audio bus|bus]]'' as a submix, a group of channels that are then added as a whole to the final mix. For instance, many drum mics could be grouped into a bus, and then the proportion of drums in the final mix can be controlled with one bus fader.<ref>[http://psbg.emusician.com/ar/emusic_mixed_signals/index.htm Mixed Signals - Studying the basics of a Mixer's signal flow] {{webarchive|url=https://web.archive.org/web/20080930221032/http://psbg.emusician.com/ar/emusic_mixed_signals/index.htm |date=2008-09-30 }}. Retrieved on 2008-08-20.</ref> A bus can often be processed just like an individual input channel, allowing the engineer to process a whole group of signals at once. Once again using the drum kit example, the use of bus-processing can enable the sound engineer to run all of the drum kit through an audio compressor effect to reduce unwanted signal peaks, rather than having to route all of the 10 or more mic signals on the drum kit individually. There may also be insert points for a certain bus or even the entire mix.

====VCA groups====
Some higher-end consoles use [[voltage-controlled amplifier]] (VCA) VCAs function somewhat like a submix but let the operator control the level of multiple input channels with a single fader. Unlike subgroups, no sub-mix is created. The audio signals from the assigned channels remain routed independently of VCA assignments. Since no sub-mix is created, it is not possible to insert processing such as compressors into a VCA group. In addition, on most VCA-equipped consoles, post-fader auxiliary send levels are affected by the VCA master. This is usually desirable, as post-fader auxiliary sends are commonly used for effects such as reverb, and sends to these effects should track changes in the channel signal level. When implemented on a digital console the same functionality may be referred to as a DCA or control group (CG), depending on the brand of mixer.

For example, if an engineer wishes to control microphones for three background vocalists at one time, muting them or changing their volume relative to a lead singer, they might create a VCA rather than adjusting all three volumes separately.  A sub-mix would be useful if they wanted to process all the singers together, adding the same amount of reverb or compression to each; but the VCA allows each channel to retain its distinctive processing while giving the engineer the ability to quickly adjust the group's volume or mute them.

===Master output controls===
The master control section is used to adjust the levels of the overall output of the mixer. The master control section on a large live venue or sound recording mixer typically has sub-group faders, master faders, master auxiliary mixing bus level controls and auxiliary return level controls. On most mixers, the master control is a fader. However, on some small mixers, rotary knobs are used instead to save space (and cost).

In a typical live sound mixing context, with a band playing at a venue, consisting of a rhythm section, solo instrumentalists and singers, the master control section allows the audio engineer to control the volume of the entire group with just one fader (for monaural mixers) or a pair of left and right faders (for stereo mixers). 

Subgroup and main output fader controls are often found together on the right-hand side of the mixer or, on larger consoles, in a center section flanked by banks of input channels. Matrix routing is often contained in this master section, as are headphone and local loudspeaker monitoring controls. Talkback controls allow conversation with the artist through their [[Foldback (sound engineering)|monitors]], [[headphones]] or [[in-ear monitor]]. A test tone generator might be located in the master output section. Aux returns such as those signals returning from external processors are often in the master section.

===Metering===
{{multiple image |align=right |direction=vertical
|image1  =API Legacy Plus 48ch.jpg |width1=130
|caption1=Meter bridge on ''[[Automated Processes, Inc.|API]] Legacy Plus'' console
|image2  =VU Meter.jpg             |width2=130
|caption2=⇑ [[VU meter]]
|footer=<hr/>⇐ [[Peak program meter]]
}}<div style="float:right;margin-right:-1.5em;">
[[File:PPM IEC 268-10 I DIN.jpg|thumb|53px]]</div>

There are usually one or more [[VU meter|VU]] or [[peak meter]]s{{efn|Peak meters often use [[LED]]s}} to indicate the levels for each channel, for the master outputs and to indicate whether the console levels are [[clipping (audio)|clipping]] the signal. The sound engineer typically adjusts the gain of the input signals to get the strongest signal that can be obtained without causing clipping. Having the gain set as high as possible improves the [[signal-to-noise ratio]]. Most mixers have at least one additional output besides the main mix. These are either individual bus outputs or ''auxiliary outputs'', used, for instance, to output a different mix to onstage monitors.

The meters may be above the input and master sections or they may be integrated into the input and master sections themselves. Meters may have needles or [[LED]]s. On meters using LEDs, there may be different colored LEDs to indicate when there is signal present in the channel's input; the audio level of the channel, typically by lighting up more LEDs; and clipping, which may be indicated using a different colored LED. In one popular color-coding system, green LEDs indicate signal presence and the audio level; one or more amber LEDs indicate that the channel is approaching clipping; and one or more red LEDs indicate clipping.

As the human ear experiences audio level in a [[logarithm]]ic fashion,{{efn|The logarithmic response applies both to [[amplitude]] and frequency.}} mixing console controls and displays are almost always labeled in [[decibel]]s, a logarithmic measurement system. Since the decibel represents a relative measurement, and not a unit itself, the meters must be referenced to a [[nominal level]]. Most [[professional audio]] equipment is referenced to a nominal level of +4&nbsp;[[dBu]], while semi-professional and domestic equipment is usually referenced to a nominal level of −10&nbsp;[[Decibel#Voltage|dBV]].<ref>{{Cite web |url=https://www.soundonsound.com/sound-advice/q-are-all-decibels-equal |title=Sound Advice > Q. Are all Decibels equal? |last=Robjohns |first=Hugh |date=October 2003 |website=www.soundonsound.com |access-date=12 February 2020}}</ref>

===Hardware routing and patching===
For convenience, some mixing consoles include inserts or a [[patch bay]] or patch panel.  Patch bays are more common in recording mixers than live sound mixers. In live sound, the cables from the onstage microphones and instrument outputs are not typically plugged directly into the mixer, because this would require a large number of individual cables to go from the stage to the mixer. Instead, the onstage mic and instrument cables are typically plugged into the stage box of a [[snake (audio)|snake]] cable which runs from the stage to the mixer. The snake is then plugged into the mixer.