Center negative DC power cables

[Ric046]

Hi, this maybe a stupid question but after being unable to find a definative answer on the web I've decided to come here to be stupid.

If I want to make a power cable for a 9vdc center negative pedal, using single core sheilded cable, do I connect the core to the sleeve and the shield to tip?

If yes then is this how power cables from the likes of voodoo labs are soldered?

I only ask because this is the opposite way round to how audio cables are made, but then I cant imagine the 9 volts should be travelling though the sheild and gnd running through the core.

Do power cables need to be sheilded to stop interference like audio cables do?

[komigenie]

Shield is always shield, NOW is up to you to solder correctly:

I think should be something like that:

[solderfumes]

You're talking about a standard Boss PSA-1-type 2.1mm barrel jack, right?  If so, then yes, the thing to do is to connect the core to the sleeve (or whatever is the "outside" of the barrel) and the shield to the centre.  As you probably know, you need a plug whose body is made of plastic, so that the casing of the plug is not connected to the +9v.

[blearyeyes]

Don't think you need shielded cable.

[alanp]

You'd only need shielding if it was profoundly filthy, unfiltered, unregulated DC power, in which case you've got problems to sort out further up the foodchain (and once the shite PSU is fixed, you don't need shielded DC power cable.)

I am just a meatworker, but interference happens when an electromagnetic field changes near a component that is sensitive to this (like, say, high gain opamps at the input of a guitar pedal.) EMF changes happen when the voltage on the wire fluctuates -- if the voltage is constant, like with a good DC source, then the EMF field will be constant. If the voltage is constantly changing, like with an AC source (power, clock source, LFO expression jack, etc), then the EMF field from the source's wires will constantly change, and thus affect the susceptible component.

But I could be talking out my arse.

[komigenie]

You'd only need shielding if it was profoundly filthy, unfiltered, unregulated DC power, in which case you've got problems to sort out further up the foodchain (and once the shite PSU is fixed, you don't need shielded DC power cable.)

I am just a meatworker, but interference happens when an electromagnetic field changes near a component that is sensitive to this (like, say, high gain opamps at the input of a guitar pedal.) EMF changes happen when the voltage on the wire fluctuates -- if the voltage is constant, like with a good DC source, then the EMF field will be constant. If the voltage is constantly changing, like with an AC source (power, clock source, LFO expression jack, etc), then the EMF field from the source's wires will constantly change, and thus affect the susceptible component.

But I could be talking out my arse.

Question was about SINGLE core shielded cable ...

[m-Kresol]

In my opinion, just use the shielded cable as you always would. GND on the shield, 9V on the core. and then just solder the plug appropriately, so shield to the tip and core to sleeve.

[alanp]

Question was about SINGLE core shielded cable ...

Yes, and the ground would be the shield (connected at both ends), with the centre conductor the V+.

I did include a disclaimer that I am just a meatworker