Editing Audio multicore cable

{{Short description|Thick cable for carrying many audio signals}}
[[File:Audio multicore cable with XLR connectors and stage box.JPG|thumb|A standard analog multicore cable with 12 sends and 4 returns]]
An '''audio multicore cable''' (often colloquially referred to as a '''multicore''', '''snake cable''' or '''snake''') is a thick cable which usually contains 4&ndash;64 individual audio cables inside a common, sturdy outer jacket. Audio [[multicore cable]]s are used to convey many [[audio signal]]s between two locations, such as in [[audio recording]], [[sound reinforcement]], [[PA system]]s and [[broadcasting]].<ref name="lsf">{{cite book |last1=Evans |first1=Bill |title=Live sound fundamentals |publisher=Course Technology |isbn=978-1-4354-5494-1 |pages=46–48}}</ref> Multicores often route many signals from microphones or musical instruments to a [[mixing console]], and can also carry signals from a mixing console back to speakers.

In [[audio engineering]], the term ''multicore'' may refer to the several things:
*an unterminated length of [[multicore cable]] intended for [[analog audio]] signals (a type of [[cable harness]])
*a terminated cable, with a multipin connector or many individual connectors
*the entire assembly of a terminated multicore cable and stage box

==Applications==

[[File:Pats drums (2941761250).jpg|thumb|Typical live use of a multicore (thick cable on stage)]]
Multicores usually create a link between the [[stage (theatre)|stage]] and [[sound desk]], or live room and control room. When used in sound reinforcement, the multicore cable runs from the [[stage box]] or [[microphone splitter]] to the [[Front of house|front-of-house]] sound desk, where it connects to a mixing console.<ref name="ilsr">{{cite book |last1=Boyce |first1=Teddy |title=Introduction to Live Sound Reinforcement |date=2014 |publisher=Friesen Press |isbn=978-1-4602-3890-5 |edition=1st}}</ref> Portable multicore cables, stored loose or on a drum, enable sound systems to be set up at temporary outdoor locations such as [[music festival]]s.<ref name="components">{{cite web |url=http://www.canare.com/UploadedDocuments/Audio%20Snake%20System%20Components.pdf |title=Audio Snake Components |website=Canare |date=13 April 2007 |access-date=21 June 2019}}</ref> Permanent installations, especially [[recording studio]]s, use stage boxes mounted in the floor or walls, with the multicore cable running through the [[ceiling]] or [[false floor]].<ref name="srp">{{cite book |last1=Shea |first1=Mike |title=Studio Recording Procedures |date=2005 |publisher=McGraw-Hill |isbn=0-07-146957-5}}</ref>

Without a snake, a rock band performing onstage, for example, would require 20 or more individual microphone cables running from the stage to the mixing console (typically located at the rear of a venue). This would be harder to set up, would cause tangled cables, and it would be difficult to identify each cable.

==Varieties==
===Terminations===
Different termination methods can be used on each end to suit the application. When individual connectors are used, three pin [[XLR connector]]s are most common, although {{convert|1/4|in|mm|2}} [[phone connector (audio)|phone connector]]s are occasionally used.<ref name="ilsr" /> An end with many individual connectors fanning out is sometimes called a ''tail'' or ''fanout'', and generally connects directly to a mixing console.

The number of connectors on a multicore is often specified by notation such as "8/4" or "8×4" for 8 sends and 4 returns. ''Sends'' usually connect a microphone to a mixing console, and ''returns'' connect a mixing console to speakers.<ref name="lsf" /> A snake with only returns is often called a ''drive snake''.<ref>{{cite web |url=https://www.harmonycentral.com/forum/forum/LivePerformanceCategory/acapella-33/382704- |title=Snake box placement |website=Harmony Central Forums |date=April 2007 |access-date=5 July 2019}}</ref><ref name="psw" />

Some systems use large multipin connectors, colloquially called ''mults'',<ref name="lsf" /> which make it easier to join snakes together{{snd}}for example, to connect subsnakes to a main stage box. This allows the system to be expanded by channel count or length. Connectors based on [[MIL-DTL-5015]] (historically MIL-C-5015) are common.<ref name="components" /> Alternatives include EDAC,{{citation needed|date=July 2019}} Burndy,{{citation needed|date=July 2019}} and DB-25<ref>{{cite web |url=https://ehomerecordingstudio.com/studio-cable-snake/ |at=Dsubs Explained |title=The Beginner’s Guide to Snake Cables for Home Recording |website=E-Home Recording Studio |access-date=5 July 2019}}</ref> connectors.
{| class="wikitable"
|+ Example balanced configurations<ref name="amphenol">{{cite book |section-url=http://www.qscomp.cz/Pdf/MIL-5015%20military%20connectors_22-23_25-37.pdf |title=Amphenol/Matrix Catalog MS/Standard MIL-C-5015 Cylindrical Connectors |section=MS/Standard: insert arrangements |pages=11–12 |url=http://www.qscomp.cz/Pdf/MIL-5015%20Matrix%20series.pdf}}</ref><ref name="components" />
|-
! Sends/Returns
! Channels
! Conductors
! [[MIL-DTL-5015]]
|-
| 8/0
| 8
| 24
| 24 pin
|-
| 8/4
| 12
| 36
| 37 pin
|-
| 12/4
| 16
| 48
| 48 pin
|-
| 20/4
| 24
| 72
| 85 pin
|}
While the sound reinforcement industry often uses proprietary premade multicores, the [[television]] broadcasting industry uses a standardized 12-channel multicore, with a common 37-pin connector on each end known as DT12.<ref>{{cite web |url=http://www.canare.com/UploadedDocuments/System%20Configuration%20Chart.pdf |title=Snake System Configuration Chart |website=Canare |access-date=24 June 2019 |date=13 April 2007}}</ref> Only 36 pins are used and sometimes the unused pin is omitted.<ref>{{cite web |url=http://whirlwindusa.com/media/uploads/downloads/manuals/dt-12.pdf |title=DT-12 Pinout |website=Whirlwind USA |access-date=24 June 2019 |date=18 December 1999}}</ref> DT12 snakes are commonly built into sports venues and stadiums for easy connection of [[outside broadcasting]] trucks.<ref>{{cite web |url=http://www.wireworks.com/Files/PDF/Wireworks_DT12_Audio_Cabling.pdf |title=DT12 Audio Cabling for Sports Broadcasting |website=Wireworks Corporation |date=19 April 2011}}</ref>
[[File:Snake cable (audio multicore cable).jpg|thumb|right|An analog multicore cable on a reel, showing its EDAC multipin connector.]]

===Subsnakes===
{{see also|Stage box#Drop boxes}}
A ''subsnake'' usually refers to a smaller multicore cable, or one not connected directly to the mixing console.<ref name="ilsr" />{{rp|272}} Subsnakes may be used to connect a few instruments from one side of the stage to the main snake, which is neater and allows for shorter [[patch cable]]s. Subsnakes use smaller stage boxes called [[Stage box#Drop boxes|''drop boxes'']].

===Composite multicores===
Composite multicores combine different types of signals in the one cable. They may contain [[coaxial]] cores for [[video]], [[twisted pair]] for data or low [[voltage]] cores for mains power. Composite multicores are usually used to connect [[professional video camera]]s, but they are now gaining usage in [[live event support]] with the introduction of the Yamaha PM1D which uses a composite cable to connect it to the [[stage box]].

===Breakout cables===
An audio multicore may also function as a type of [[breakout cable]], sometimes referred to as a ''fan'' or some variation, if it has a compound (multipin) connector on one end and individual connectors on the other.<ref name="components" /><ref>{{cite web |url=https://www.proaudiola.com/help_options.asp?ID=69 |title=MG-2936 Cable Length |website=Pro Audio LA |access-date=5 July 2019}}</ref> This is more common in short multicores meant for in-[[studio]] connections, such as [[audio engine]]s, [[analog-to-digital converter]]s or [[digital mixing consoles]].<ref>http://www.yamahaproaudio.com/products/interfaces/ygdai_cards/index.html Yamaha Mini-YGDAI interface cards</ref>  Multicore cables may also connect to either the front or back of [[patch panel]]s, when the patch panel is used as an access point or breakout box for connecting external inputs and outputs.<ref name="psw" />

== Cable construction ==
:''In this section, '''core''' refers to a single channel within a multicore cable, whilst '''conductor''' refers to a single wire.''

=== Core conductor arrangement ===
The vast majority of audio multicore cables consist of a number of twisted-pair [[copper wire]]s, suitable for [[balanced audio]].<ref name="ilsr" />{{rp|50}} To reduce noise, the shield of each channel is often isolated from the other shields. Balanced connections may use XLR connectors or {{convert|1/4|in|mm|2}} TRS phone connectors {{see above|{{section link||Terminations}}}}.

The broadcast industry tends to use audio multicores containing [[star quad cable]]s, due to their increased rejection of radio-frequency interference.<ref>{{cite web |url=https://www.soundonsound.com/sound-advice/q-whats-special-about-star-quad-cable |title=Q. What’s special about star-quad cable? |website=Sound On Sound |date=November 2009 |access-date=5 July 2019}}</ref> Some multicore cables designed for unbalanced audio are made, and they contain a number of single-core screened cables.<ref>{{cite web |url=http://www.crecso.com/how-to-select-right-multicore-cable/ |title=Know How To Select Right Multicore Cable: Role of Signal System in Multicore Cable Selection |date=9 March 2018 |website=Cresco |access-date=5 July 2019}}</ref>

=== Core screening ===
{{see also|Shielded cable}}
The individual cables inside the multicore are usually screened independently.<ref>{{cite web |url=https://thenoizeworkstechnical.blogspot.com/2012/10/stageboxes-multicores-balancing-and-di.html |title=Stageboxes, Multicores, Balancing and D.I. Boxes. Part One |website=Noizeworks Live Sound Technical Stuff Blog |date=20 October 2012 |access-date=5 July 2019}}</ref> This reduces [[crosstalk]] between cables and also enables each cable to have a screen or ground that is isolated from other cables, significantly reducing the possibility of [[Ground loop (electricity)|ground loop]]s which can cause unwanted hum.

A foil-screen is typically used, comprising thin aluminium wrapped around the group of conductors. An uninsulated drain wire is contained inside the screen to facilitate ground connection.<ref name="psw">{{cite web |url=https://www.prosoundweb.com/topics/analog/clear_path_analog_snake_systems/ |website=ProSoundWeb |title=Analog Snake Systems And Their Applications |publisher=EH Publishing |last=Janis |first=Peter |date=6 October 2015 |access-date=5 July 2019 |page=1}}</ref>{{rp|1}} A less common construction is a lapped or braided screen comprising thin wires wrapped around the conductors. This gives improved flexibility, but less effective screening.<ref>{{cite web |url=https://www.soundonsound.com/sound-advice/audio-cables-wiring |title=Audio Cables & Wiring: Frequently Asked Questions |website=Sound On Sound |last=White |first=Paul |date=January 2002 |at=Q. Are all screened cables much the same, or are some better than others? |quote=Foil-screened cables are rather rigid and don't take kindly to sharp bends, but they do offer excellent screening properties and smaller-gauge cables are available for such jobs as patchbay wiring and permanent cable runs. Many multicore cables also use foil screening, and it's important not to coil such cables too tightly.}}</ref>

=== Core insulation ===
This describes the method used to isolate the screening between individual cores; two approaches are common. The first method has an extruded plastic sheath around each individual core, making the multicore appear like a number of individual audio cables bundled together inside an outer sheath.<ref>{{cite web |url=https://www.jaycor.co.za/wp-content/uploads/2017/07/JAYCOR-Broadcast-Connectivity-Solutions-2017.pdf |quote=Individual aluminium-mylar screen over each pair; Individual PVC sheath over each screened pair; Nitrile (High Flex) PVC Sheath |title=Broadcast Connectivity Solutions |website=Jaycor International |access-date=5 July 2019}}</ref> The second method dispenses with the individual sheath and typically wraps the screening with very thin plastic; in some cases this plastic is bonded to the foil sheath.<ref>{{cite web |url=https://info.belden.com/hubfs/resources/technical/product-brochures-bulletins/analog-audio-snake-cables-product-bulletin.pdf |title=Product Bulletin 502: Belden Analog Audio Snake Cables |website=Belden |access-date=5 July 2019 |at=Banana Peel Audio Snake Cables}}</ref>

The individually sheathed construction has the advantage that individually cores can easily be terminated to individual connectors at the ends of the cable. Its disadvantage is that the size and weight of the cable are increased. When a cable without individual sheaths has to be terminated to multiple connectors, it is common practice to create individual sheaths using heat-shrinkable tubing.

=== Overall screening ===
A small number of multicore cables compromise twisted-pairs with only an overall screen. These are virtually obsolete and typically only found in older broadcast installations; the use of individual screens is now virtually standard. Some multicore cables do contain an overall braid screen in addition to the individual screens on each core. This also increases the mechanical durability of the cable.

=== Overall insulation ===
Multicore cables usually have a thick PVC or [[cross-linked polyethylene]] sheath protecting the bundle of individual cables.<ref name="mogami">{{cite web |url=http://www.mogamicable.com/category/bulk/snake/ |title=Snake Cables (Multicore Microphone Cables) |website=Mogami Cable |publisher=Marshall Electronics, Inc. |access-date=6 July 2019}}</ref> The PVC sheath is extruded around the inner cables, and solidifies to hold the cables in a tight group. This stops the cables from coming out of their tight braid (a phenomenon known as ''corkscrewing''),<ref name="psw" /> and absorbs mechanical stress such as a person stepping on the cable.<ref name="ilsr" />{{rp|243}} A typical 48 channel multicore has an outside diameter of {{convert|1|in|mm}}.

=== Core identification ===
Different cable manufacturers use different methods of identification for the shielded pairs of cable. [[Belden (electronics company)|Belden]] have a sequenced color code and a number for each of the conductors in their products of up to 52 pair cables;<ref>{{cite web |url=http://www.techsheet.com/BroadcastInstallShop/pdf/belden/colourcodes.pdf |publisher=Belden |title=Belden Color Code Charts |access-date=5 July 2019}}</ref> for their plenum cables each pair is covered with their patented Beldfoil shield that is only [[conductive]] on the inner surface.{{citation needed|date=July 2019}} For their portable cables they use a [[French braid]]. [[Canare]], [[Mogami Cable|Mogami]],<ref name="mogami" /> [[Clark Wire & Cable]] and [[GEPCO]] mark numbers on the [[PVC]] [[Electrical insulation|insulation]] of the individual pairs.

== Digital alternatives ==
{{main|Stage box#Digital stage boxes}}
Whilst traditional analog multicore cables are common in sound engineering, the advent of [[digital mixing console]]s have made so-called ''digital multicores'' favorable for many scenarios where multiple signals need to be run a long distance.<ref name="ilsr" /> Whilst not technically a multicore cable, this newer system performs the same function, but comprises a [[Stage box#Digital stage boxes|digital stage box]] connected directly to a mixing console through a single [[twisted pair]] or [[fiber-optic cable]]. The stage box converts between [[analog signal|analog]] and [[digital signal|digital]] signals with [[digital-to-analog converter|DA]] and [[analog-to-digital converter|AD]] converters.<ref name="lsf" />

This has the advantage of being much easier to set up and move, since only a single small cable needs to be run. [[Digital audio]] signals are also virtually insusceptible to [[electromagnetic interference]], which is a great advantage in some applications such as long cable runs.<ref name="taoe">{{cite book |last1=Horowitz |first1=Paul |last2=Hill |first2=Winfield |title=The Art Of Electronics |edition=2nd |publisher=Cambridge University Press |date=1989 |pages=[https://archive.org/details/isbn_9780521377096/page/471 471]–473 |url=https://archive.org/details/isbn_9780521377096 |url-access=registration |quote=digital analog noise. |isbn=0521370957}}</ref> Sometimes the only cable run between the stage and sound desk is a single digital cable, and all audio processing occurs in digital format at the mixing console and stage box.

Common protocols used for digital multicores include [[audio over Ethernet]] and [[AES10]] (MADI).<ref>{{cite journal |last1=Frink |first1=Mark |title=Cat5 Digital Snake Stage Boxes |journal=FOH Online |accessdate=8 July 2019 |date=February 2012 |page=37 |url=http://www.fohonline.com/images/stories/12/02/current/37-39.200.1202-savior.pdf}}</ref>

==References==
{{reflist}}

[[Category:Audio electronics]]
[[Category:Signal cables]]