Mixing console
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In professional audio, a mixing console, mixing desk (Brit.), or audio mixer 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 signals, depending on the type of mixer. The modified signals (voltages or digital samples) are summed to produce the combined output signals.
Mixing consoles are used in many applications, including recording studios, public address systems, sound reinforcement systems, broadcasting, television, and film post-production. An example of a simple application would be to enable the signals that originated from two separate microphones (each being used by vocalists singing a duet, perhaps) to be heard through one set of speakers 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.
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Structure
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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). 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 are used to send to and return from external effects, such as a delay or reverb which should only affect one singer's voice.
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).
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.
Finally, there are usually one or more VU or peak meters 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 monitors. The operator can vary the mix (or levels of each channel) for each output. Most mixers also have equalizers of varying sophistication.
As audio is heard in a logarithmic fashion (both amplitude and frequency), mixing console controls and displays are almost always in decibels, 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.
Toshimaru Nakamura is perhaps the first person to use a mixing board as a musical instrument.
Most, but not all, audio mixers can
- add external effects.
- use monaural signals to produce stereo sound by adjusting the position of each signal on the sound stage (pan and balance controls).
- provide phantom power (typically 48 volts) required by some microphones.
- create an audible tone via an oscillator, usually at 440Hz, 1 kHz, or 2kHz
Some mixers can
- add effects internally.
- interface with computers or other recording equipment (to control the mixer with computer presets, for instance).
- be powered by batteries.
Examples of mixing consoles and their manufacturers
- ADT-Audio [1] (http://www.adt-audio.com/)
- Allen & Heath
- Audient
- Behringer
- Eurorack
- Harrison [2] (http://www.harrisonconsoles.com/)
- MPC - a console for film post-production
- LPC - a console for live performances
- TVD - a console for TV & radio broadcasters
- Inter-M
- Lawo (http://www.lawo.de)
- Mackie
- Midas [3] (http://www.midasconsoles.com/)
- AMS Neve
- Solid state logic
- Rane
- Samson
- Shure
- Soundcraft
- Studer [4] (http://www.studer.ch/)
- Tascam
- Yamaha
See Also
External links
- Brain, M. (n.d.). A sample mixer. In How band equipment works. Retrieved January 5, 2004 from http://entertainment.howstuffworks.com/band-equipment5.htm
- Glossary of mixer terms (http://music.concordia.ca/Programs/Electroacoustics/mixer/Mixer_Terms.html)
- Mixer how-to (http://www.musicianstechcentral.com/mixer.html)
- Mixing Consoles 2003 - Reviews many higher-end systems (http://mixonline.com/ar/audio_mixing_best/)de:Mischpult