multi-core ... on drum or not?

[peternewman]

Care to expand a bit further RGSD?

[RGSD]

So... when you coil a cable, you do a loop, then a back loop - to opposite the effects of interference. If it is on a drum, then the drum doesn't do the back loop and therefore creates a continuous coil susceptible to interference.

 

Exactly why you would figure of eight a cable.

[Matt Riley]

The only reason I know to figure 8 cables is when you're using big power (63 amp plus) and you don't want to risk creating a big hot electromagnet out of it. It is, to the best of my knowledge irrelevant to do it to signal cables. However lots of small drum mounted domestic extension leads need to be unwound for their rating to be accurate, and are usually fairly well labelled to that effect, so maybe this is where that particular myth came from.

 

M

[paulears]

Figure-8'ing any cable that is required to be pulled out is the only way of temporary storage that doesn't put twists in the cable? Really common with chunky snakes and if you've ever worked with a BBC OB tender they'll spool off their long camera cables to fig-8's on the floor, and if the BBC do it with their experience, it's good enough for me!

 

I think I've missed the Physics lesson where interference was an issue?

[mervaka]

individually shielded, balanced cables aren't succeptible to that much crosstalk.. paul's got the right idea for fig8 windings, it just pulls out straight. its what I do in my suitcase. I dont fancy dicking around pulling out twists in an inch thick cable when I have an hour or so to set a PA up.

[Simon Lewis]

So... when you coil a cable, you do a loop, then a back loop - to opposite the effects of interference. If it is on a drum, then the drum doesn't do the back loop and therefore creates a continuous coil susceptible to interference.

 

But twisted pair cable already counteracts magnetic interference? Although there are some drawbacks to foil screen/drainwire assemblies, screening is usually plenty good enough for audio work.

 

A concurrent post has been automatically merged from this point on.

 

We are looking at replacing our multi-core, and the main question is do we stick with a drum or not?

 

A 50m 32 pair multi can work with a drum fairly well. Whilst I accept that larger cable systems (especially when two or more cables are bunched) benefit from being coiled in a trunk, a decent drum is still quite usuable at this size and smaller.

 

Things to look for:

 

- either a XLR input plate on the drum flange, or a neat method of connecting the inner tail to a stagebox

- a good winding handle

- a drum brake that doesn't snap off on its first outing

- possibility of terminating the cable with a multipin, and leaving a multipin to tails in the mixer case.

- possibility of mounting the drum in a wheeled flightcase for protection and ease of transport

 

Canford and VDC sell some larger drums (CD3, Marcaddy etc.).

 

Simon

[johndenim]

Leaving a multicore half coiled will make no difference, as long as it is only signals going through it.

 

Are you thinking of a B&Q mains drum?

Whatever you get OP, 50m is going to be heavy!

 

John Denim.

[ruibr]

Hi,

 

I bought a drum multicore back in the day. Cheap too, from Omnitronic. Well, first it started that I had to disassemble the mechanical brakes on the neutrik plugs because once you got a mic cable in, it just wouldn't come out! Now I have about 10% of channels either not working at all, or not conducting phantom power, or getting noses into the sound,etc...

We keep saying that it will make for a nice bonfire once we get a new digital snake.

 

I can't really go into the phisics of the thing (because I don't know them!!), but from my experience, they are to be avoided. Especially cheap ones.

So if you're going to spend money, make sure you don't spend it twice, like I'll have to do.

 

Good luck with whatever choice you make.