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In professional Audio , a mixing console, Digital Mixing Console , '''mixing desk''' (Brit.), or '''audio mixer''', also called a '''sound board''' or '''soundboard''', is an Electronic device for combining (also called " Mixing "), routing, and changing the level, Tone , and/or dynamics of audio signals. A mixer can mix Analog or Digital Signal s, depending on the type of mixer. The modified signals ( Voltage s or Digital Samples ) are Sum med to produce the combined output signals. Mixing consoles are used in many applications, including Recording Studio s, Public Address System s, Sound Reinforcement System s, Broadcasting , Television , and Film Post-production . An example of a simple application would be to enable the signals that originated from two separate Microphone s (each being used by vocalists Singing a Duet , perhaps) to be heard through one set of Speaker s simultaneously. When used for live performances, the signal produced by the mixer will usually be sent directly to an Amplifier , unless that particular mixer is “powered” or it is being connected to Powered Speakers . STRUCTURE The input strip is usually separated into these sections:
On the Yamaha Console to the right, these sections are color coded. Each signal that is Input 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 input, and many have RCA or quarter-inch Jack Plug line inputs. Below each input, there are usually several rotary controls (knobs, pots). The first is typically a ''trim'' or ''gain'' control. The inputs Buffer the signal from the external device and this controls the amount of amplification or attenuation needed to bring the signal to a Nominal Level for processing. This stage is where most noise or interference is picked up, due to the high gains involved (around +50 DB , for a microphone). Balanced inputs and connectors, such as XLR or Tip-Ring-Sleeve (TRS) quarter-inch connectors, reduce interference problems. There may be ''insert'' points after the buffer/gain stage, which send to and return from external processors which should only affect the signal of that particular channel. Insert points are most commonly used with effects that control a signal's Amplitude , such as Noise Gate s, Expander s, and Compressor s. The Aux sends send the incoming signal to external devices. Aux sends can either be pre-fade or post-fade, in that the level of a pre-fade send is set by the control, whereas post-fade depend on the position of the channel fader as well. Aux sends can be used to send the signal to an external processor such as a reverb, which can then be routed back through another channel or designated aux returns on the mixer. These will normally be post-fader. Pre-fade auxs provide a monitor mix to musicians onstage, this mix is thus independent of the main mix. Further channel controls affect the Equalization of the signal by separately attenuating or boosting a range of Frequencies (e.g., Bass , midrange, and Treble frequencies). Most large mixing consoles (24 channels and larger) usually have sweep equalization in one or more bands of its Parametric Equalizer on each channel, where the frequency and affected bandwidth of equalization can be selected. Smaller mixing consoles have few or no equalization control. Many users recommend that the equalization be set so that if the speaker has a high frequency, elevate the lows and bring down the highs and vice versa for a low frequency speaker. This allows a little of amplication to be added to the general effects. However, this can distort the signal's EQ. Some mixers have a general equalization control (either graphic or parametric). Each channel on a mixer has an audio taper pot, or Potentiometer , controlled by a sliding volume control (''fader''), that allows adjustment of the level, or amplitude, of that channel in the final ''mix''. A typical mixing console has many rows of these sliding volume controls. Each control adjusts only its respective channel (or one half of a stereo channel); therefore, it only affects the level of the signal from one microphone or other audio device. The signals are summed to create the main ''mix'', or combined on a ''bus'' as a submix, a group of channels that are then added to get 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). There may also be ''insert'' points for a certain bus, or even the entire mix. On the right hand of the console, there are typically one or two master controls that enable adjustment of the console's main mix output level. In recent years, with the demand for larger consoles, the main mix and submix controls have started to be placed in the center of the console. The idea behind this is that larger consoles often need two people to operate them, and that the first channels used are often the lower numbered channels. With the mains and subs in the middle, two people can easily control their own set of 16, 24, or 32 channels as well as easily reach the main controls. It is very rare to see this setup on boards with 24 or fewer channels. Finally, there are usually one or more VU or Peak Meter s to indicate the levels for each channel, or for the master outputs, and to indicate whether the console levels are overmodulating or Clipping the signal. 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 on-stage Monitor s. The operator can vary the mix (or levels of each channel) for each output. As audio is heard in a logarithmic fashion (both amplitude and frequency), mixing console controls and displays are almost always in Decibel s, a logarithmic measurement system. This is also why special audio taper Pots or circuits are needed. Since it is a relative measurement, and not a unit itself (like a percentage), the meters must be referenced to a nominal level. The "professional" nominal level is considered to be +4 DBu . The "consumer grade" level is −10 DBV . For convenience, some mixing console racks contain a Patch Bay or patch panel. These may be more useful for those not using a computer with several plugins on their software. Most, but not all, audio mixers can
Some mixers can
VIRTUAL MIXING CONSOLES Increasingly, the mixing process is performed on screen, using computer software. Often, tracks are built up individually or in groups, the whole composition only being playable after that stage in the process. This process requires an Audio Interface that converts analog audio into a digital format that can be used by the software. Pro Tools has offered a complete hardware and software package that has been the standard in the professional audio industry for many years, although other hardware manufacturers and software applications have made in-roads in recent years. APPLICATIONS Dub producers/engineers such as Lee 'Scratch' Perry were perhaps the first musicians to use a mixing board as a Musical Instrument . Public address systems will use a mixing console to set microphones for different speakers to the correct level, and can add in recorded sounds into the mix. A major requirement is to minimise audio feedback. Most bands will use a mixing console to combine musical instruments and vocals to the correct level. Radio broadcasts use a mixing desk to select audio from different sources, such as CD players, telephones, remote feeds, or prerecorded advertisements. MIXING CONSOLE MANUFACTURERS
SEE ALSO EXTERNAL LINKS
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