Basically, the shields should only be connected at only one end of the wire (except mic lines).
Yes because it will prevent ground loops, no because it allows radio frequency pickup! It's the real pain with grounding arrangements in studios. If possible you should always connect the screen right the way through, which is fine when running to equipment with a ground lift switch but causes problems when it doesn't. Or when it does have a ground lift switch but it has a horrible switch mode supply inside which puts noise between the mains ground and the signal ground anyway.
So yes we often do end up breaking the screen, but we really shouldn't. Particularly as studios get ever noisier at the RF end with every piece of kit having switch mode supplies and a few processors chuntering away in it.
There is a kludgy solution to break the screen but put a small capacitor (say around 1nF) across the break, so it conducts RF but doesn't conduct 50Hz/60Hz.
The real problem is that if equipment (desks and outboard) were designed / built for this to all work properly then no-one would be available to afford it. (Since leaving the audio industry a lot of my time has been spent with people who solve grounding and shielding problems all day for other industries, in fact I've long been involved with writing international standards on this stuff which is a thankless and horrible task.) What we
want is the performance of medical equipment, which is really, really good at managing this stuff (it has to be!), but is eye-wateringly expensive. So we're left with trying to connect to the dodgy "classic" reverb, or a single coil unshielded Strat...which would make a professional grounding and shielding engineer say "you don't want to be doing that"...sorry, yes we do! So back to the rules of thumb and keep trying things until it works...
By the way, re ground spikes, and mesh in a lake etc, it's rarely the ground to earth that's a problem unless you're right next to a radio transmitter or you're running a studio across several different buildings. The whole studio can float up and down, and that's absolutely fine. The challenge is to either stop the noise generated
in the studio from circulating in the studio at all, or to make sure it doesn't circulate through anything critical by keeping loops and aerials short, or by cancelling out any noise that does circulate by balancing.
Just seen the post about "which end to disconnect": any two audio EMC engineers will give you two different answers on this (this has been argued about at least back to the 1980s, and probably longer). An instrumentation EMC engineer will say as above "don't cut it at all". I'd say the actual answer is "it all depends" - on where the RF source is that you're protecting against, and which piece of equipment has the best RF ground. Which you won't know until you try. As above, grounding and shielding is a very specialist subject, people who do it that's all they do. So take
advice from people who've got good experience, but don't treat it as a "rule" unless they actually are EMC professionals.
Cheers,
Andy
