Multicore
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Multicore (German: "Mehrfachkern") is the name of special cables in sound and lighting technology in which numerous (up to 48) individual signal lines, called "channels" or "paths", are bundled in a single cable jacket. Multicores can be used in concert events and recording studios . Multicores simplify the assembly and dismantling of a system by saving the laying of numerous individual cables and help to avoid cable clutter .
use
Multicores are used both in mobile event technology and in permanently installed systems. Bundled cables are easier and faster to lay than individual cables, and the bundling also increases the stability against mechanical stress (tension, pressure, kinking). Multicores are used, for example, to simplify the cabling of several external effects devices between electrical musical instruments and audio amplifiers . Another purpose of multicores is to route several electrical audio signals from a concert stage to a mixer , which is usually positioned in the audience room, and back ( front of house ) . Such cable routes can be over 100 meters long , for example at large open-air concerts.
Assembly
At the ends, the multicore usually has to be "broken down" into the individual channels. There are two structural solutions for this:
- Stagebox : The multicore ends in a stable connection box that has connectors for the individual channels. This form is mostly used on stage. The microphone cables of the individual sound sources are all led to the stage box and plugged in there. The stage box can also be part of a cable drum onto which the multicore is wound.
- Console resolution : The multicore is spliced over a length of 1… 2 m into the individual channels, the ends of which have individual connectors. This shape is also known as a cable whip and is more practical on the mixer, since all the plug connections are close together.
Audio multicores are usually divided into “send” and “return” channels: the first lead from the stage to the mixer, the second lead in the opposite direction. The only difference is in the connectors, the cable routes themselves are not defined in the signal direction and can easily be "rotated" with plug adapters.
Often there are ground lift switches (interrupting the shielding) on the stage box for individual channels, as well as further multipin connectors for looping through the signals. There are also seldom stage boxes with built-in transformers for electrical isolation.
Both forms of resolution can be permanently installed on the cable or contacted with multipin connectors. Permanently attached resolutions are structurally simpler and cheaper, but have disadvantages: When laying cables, at least one of the cable ends must be routed through the entire cable route; when stowing the multicore, the resolutions are heavily stressed.
Frequently used multipin connectors for multicores are the rectangular Harting and the round Socapex connectors. The smaller and cheaper tab headers can also be found mainly at broadcasters . There is no standardized standard for the selection and assignment of the connectors, the versions vary from manufacturer to manufacturer.
Signal routing and shielding
The signal routing in a multicore is usually symmetrical due to the long transmission paths. The signal-carrying conductors in multicores are individually shielded against interference from electromagnetic fields by metal sheaths . In the case of high-quality multicores, the shielding is usually double; In addition to the overall shield that surrounds the entire cable harness, there are individual shields for each signal-carrying wire pair. We also speak of multicores with “individual ground”, since the individual shields that are at ground potential of the respective channel are not electrically connected. Thanks to the independent ground potentials, it is possible to eliminate hum loops by setting ground lifts on individual channels.
Special types of construction
There are some special forms of multicores that differ from the design described above:
- As Submulticore (also "subcore", "Subsnake", "stage sub-distribution") refers to smaller Multicores short length (usually no more than ten meters) and only a few (usually eight to ten) channels. Submulticores are used to transport several signals on larger stages to the stage box without having to lay many individual cables. In the case of submulticores, due to their small size, it is common for the breakout cable and stage box (often referred to here as a “plug box”) to be firmly connected to the cable. Another use is the use on stages in small event rooms.
- An insert multicore (often referred to as an “insert whip”) is a short multicore that combines several insert cables . It is used to connect the mixer to signal processing equipment in the siderack .
- There used to be multicores for control signals in lighting technology. Analog control signals, mostly in 0 to 10 V technology, were transmitted from the lighting desk to the dimmer. Nowadays this method has been almost completely replaced by digital DMX transmission. Instead, analog multicores can also be used to reduce the cables of several DMX universes to one.
- Load multicores for lighting technology are still in use . These are multi-pole load cables that act as power lines to connect dimmers and lights. Load multicores are usually assembled with heavy industrial connectors ("Hartings") and are broken down into their individual channels on the consumer side via plug boxes. Last multicores with three, six, eight and twelve channels are common. Cross-sections of 1.5 or 2.5 mm² are mostly used.
- Digital multicores are gradually replacing the very expensive, heavy and error-prone analog multicores in sound engineering. Although no standard has yet been able to establish itself, there are now numerous useful concepts that are mostly based on Firewire , Ethernet or fiber optic cables (“Optocore”). In contrast to computer technology, resistant cables are used that are mechanically up to everyday life on the stage. Like all digital components in audio technology, digital multicores have problems with latency times that need to be minimized. In addition, the signals must be digitized at the point of origin (stage). The previous problem that the level adjustment required for this had to be carried out and monitored by an (additional) technician on the stage before the A / D conversion, which was not practical, especially for smaller events, is now solved by remote controllable preamplifiers.
- Strictly speaking, multi-channel loudspeaker lines ( e.g. Speakon ) can also be referred to as multicore.
- In the field of sound, light and video technology, there are numerous other special cables that combine several individual lines, for example power and data lines. These cables are often referred to as hybrid cables .
See also
- Cable harness - stationary solution for bundling cable harnesses
literature
- R. Beckmann: Manual of PA technology, basic component practice. 2nd edition, Elektor-Verlag, Aachen, 1990, ISBN 3-921608-66-X
- Roland Enders: The home recording manual. 3rd edition, Carstensen Verlag, Munich, 2003, ISBN 3-910098-25-8
- Michael Ebner: Lighting technology for stage and disco. 1st edition, Elektor-Verlag, Aachen, 2001, ISBN 3-89576-108-7