8 Channel Multicore Analog Snake

in Blog

25 October 2009

DIY Multicore 14

A home-made 8 channel snake using high quality components.

DIY Multicore 13

Brief
Build the most robust and high quality 50m snake as possible. The snake should be housed on cable drum, be serviceable and exhibit excellent electrical and physical characteristics.

The snake will be used for a variety of purposes, but mainly carrying low-level microphone signals in location recording and small-scale sound reinforcement jobs.

Choosing the right cable

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The cable must be extremely robust, have a low physical profile and provide a good level of insulation from electrical interference. There are a number of high quality multicore cables available from companies such as Sommer Cable, Mogami, Belden and Canford Audio. However, being impressed with the Van Damme cables I have used in the past, I chose Van Damme Black Series multicore for this project. The Black Series was designed specifically for demanding touring applications and as such is ideal for this snake.

Preparing the cable
Since Van Damme Black Series multicore cable was probably designed to be terminated into multipin connectors rather than directly into XLR connectors, the inner pairs are not pre-jacket. Since this snake will fan out into XLR connectors at one end, each inner pair needs to be jacketed to provide protection from the outside world.

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Jacketing the inner pairs

To do this, 4.8mm flexible polyfin heatshrink was used (see photograph above). A further jacket of 3mm-6mm expandable braided sleeving was added to provide even more protection and to help prevent the fan-out from tangling. 6.4mm (before shrinking) adhesive-lined heatshrink was used to fix both ends of the sleeving onto each pair. This extra layer of heatshrink also acts as a strain relief for the XLR connector plugs (see below).

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Braided sleeving held in place with adhesive-lined heatshrink

Where the inner pairs leave the original multicore cable jacket, 25.4mm (before shrinking) adhesive-lined heatshrink was added as a strain relief.

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XLR connectors
Neutrik NC3MXX-B male XLR connectors with gold contacts were used. Colour-coded boots were used for speedy connections in bad lighting conditions.

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One of the inner pairs ready for the XLR connector

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Inner pair number 3 (orange boot) with XLR connector

The cable drum and connection panel
After looking at a number of cable drums, an all-steel cable drum with a friction drum-brake made by Canford Audio was chosen. These drums come in three styles – I chose the one that comes with a plastic blanking plate for connectors. Due to the difficulties of drilling the precise holes for the XLR connectors, and because a plastic connection panel is not particularly strong, I disposed of the plastic panel, and decided to have a bespoke aluminium panel custom made.

Designing the connection panel
After a lot of thought and sketches, I began layout the panel using free software I found online.

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A printout of the design

I chose to have the panel cut out of 3mm matt black anodised aluminium. The lengh of the snake, the XLR connectors and an identifier ‘tag’ were also engraved and infilled white. These markings should never wear away.

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DIY Multicore 9

Panel connectors
Neutrik NC3FD-LX-B XLR panel connectors were used. This particular connector has gold contacts and a steel inner ring that surrounds the plastic insert to prevent it from wearing away when a connector is inserted at the wrong angle and twisted until it slots into place.

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XLR panel connectors ready for soldering

I jacketed the inner pairs at the panel end of the cable, thinking that this would strengthen them. In retrospect, this was probably not required. The multicore cable is held into the cable drum with a tight fitting grommet.

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Cable soldered onto connectors

Finishing touches
A Rip-tie velcro cable tie is permanently affixed to the carrying handle of the cable drum. This is to prevent unraveling by holding the cable in place when the drum is fixed in position.

A padded cover will protect the cable drum from light knocks when in transit. This will have a slit in the top so the carrying handle is still accessible.

A small pouch will house the 8 XLR plugs when in storage, and when reeling in the snake to prevent damage and to help keep them clean. For now, a leather pencil case will do.

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The finished product

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