Single Core (Shielded) LV Cabling for Audio Equipment

Morning Again


Just following up on the comment made by Andy (Ajjewsbury)

The much more usual approach these says is to have a single earthing system but with as many interconnections as possible - so you end up more with a mesh or grid of earth conductors rather than just a tree or ring - lots of metalwork bonded (whether required for shock protection or not) and possibly screens of small cables paralleled with a much larger conductor to ensure they're no damaged by large (e.g. fault) currents as well as reducing the overall impedance.

I am familiar with EBB installations (equipotential bonding busbar), as used within Healthcare installations such as MRI's, CT Scanners etc., so can I take it that this is what you are suggesting (or very similar) is common practice in this instance?


Once more, thanks in advance for any response.


Regards


Adrian B.

I am familiar with EBB installations (equipotential bonding busbar), as used within Healthcare installations such as MRI's, CT Scanners etc., so can I take it that this is what you are suggesting (or very similar) is common practice in this instance?

It's the approach that BS EN 50310 takes (as Graham mentioned earlier)  - there are a number of methods - bars, or rings that go right around the building (or room) or just lots of small connections - which works best can depend on a lot of factors not least the physical layout of the system that needs protection (e.g. whether it's a single room, or a whole floor or a building of many floors; and whether the equipment is tightly packed, or scattered in several small groups or thinly spaced)


  - Andy.

Are you sure you are addressing the problem the "specialist" is concerned about? It is unlikely that noise radiated by mains cables will get into studio balanced audio cables if it is all installed properly. Good separation of mains and signal cables is should be managed carefully, and any problem is unlikely. The next step is to fit "proper" mains filters to the power entering the studio area, but these are both expensive and have very high earth leakage current, so excellent earthing is important. As far as possible there should only be one connection between the mains Earth and the audio equipment signal earth, to prevent circulating earth current in the audio cables. This may mean that class 1 equipment needs to have Earth cable connections removed, although it will be earthed via the audio cables. This is the kind of area where you really do need a proper studio Engineer, who has done all this before, to ensure that the finished system is safe. Studio systems do not usually use any single core screened cables for anything except guitar leads to the DI box.