Do you have to connect cable shields?

I posted this question recently over on HFC, but as I've been told conflicting information I thought I'd check with you guys too. To put this in context I recently tried a pair of Frontfloater's Mithril interconnects, which I was very impressed with and are clearly better than the Musical Fidelity Nu-Vista's I was thinking of replacing. The thing is these have a Mylar foil plus
copper braid screen around the two main silver conductors, but this is not electrically connected at all. Naively I was wondering if this might be missing a trick and that these cables could potentially be even better with this linked up to the return path at the source end?

 

Link them to the ground at the amp end, not the source

 

It's called 'Physdo balanced', however it can have a detrimental effect on Some cables too. WM

 

Hmmm... now I know you're going to get some affects both end whatever, but I thought the idea was that if you linked the shield up at the amp end then the RFI would basically be passed into the amp and amplified, if anything being worse than just having an unshielded cable? If you can dump most of the RFI into the output impedence of the source that I'd naively have thought would be better?

Of course if I could connect the shield to an actual earth, rather than the signal return, that would clearly be best, but that isn't really practical, so what I'm wondering about is a semi-balanced design.

 

Really. I suppose if there wasn't an RFI issue that makes sense, because it would be going from a balanced design to a semi-balanced one. Given I liked the cables as they were when I tried them it might be wise just to not worry about it...

 

Martin, are these XLR's then?, Rca's cannot be balanced as the only have 2 connection points, hence the Physdo balancing of joining one end, a Balanced cable with have a Ground/signal and inverted signal pins and 3 connection points.
Just one other thought, they are many ways of RFI rejection other than braids. WM

 

Nope, sorry, standard RCAs. I'm not perhaps using the term balanced as it's usually used in HiFi terms, but by balanced I meant that the signal and return paths are identical. I think that is strictly what is meant by balanced, but I'm very open to be corrected. This is only a question of terminology and so totally irrelevant anyway as long as you now know what I mean


If you're including a screen in your cable then the only way for it to be balanced is to have the three connections of an XLR connector. If you don't worry about a screen then a cable formed from two identical wires would also have an identical signal and return path. The latter being what you'd have with the Mithril's and what I meant in my confusing (sorry) last post.

 

I'll try again first post vanished ?

Pseudo Balanced cables are IMO best withe the shield connected at the source end. This should keep the nasties out from the the rest of the chain.

 

Zanash - cheers for your comments. I keep meaning to pull out an old electromagnetism textbook and actually think this through, but do you happen to know if an unconnected shield serves any purpose at all? I have a suspicion that it doesn't...

 

Oh yeah, I meant to put this in my last message...

Of course no matter how identical the forward and return wires are, an RCA connection is never going to be balanced by any definition, since the forward and return connections are different. Probably to obvious an error on my part for anyone to bother to point out, but I've realised now at least...

 

I bought a few pairs of different 'grades' of Monster Audio IC's a few years ago when visiting the US , mostly due to the fact that they where so much shockingly cheaper over there compared to the UK. Quite a few of them had this type of wiring geometry, with basically a twisted pair of conductors surrounded by a foam dielectric and then a braid/foil screen which was electrically connected at one end only. These cables actually had little arrows printed on them and i remember the literature on the packing carton recommending that the connected sheild should be at the source end , with the floating sheild at the amp.
Whenever i have made DIY IC's using sheilded twisted pair I have always connected them up in this manner.

I should add that I have often found over the years that my IC's had been accidentaly connected up 'the wrong way round' , often for long periods of time. I can't say I actually noticed any difference to the sound , certainly no night & day diff's anyway.

Another small point to ponder is that i believe the Electrical signal travelling down 'directional' IC and speaker wires is Alternating Current. ie The electrons flow one way then the other many times per second.

HTH.
Regards
S&C.

 

This pseudo balanced screen connection approach is the time where you can actually end up with a directional cable IMO. I tried some VDH D102MkIIIs once, which use this approach I believe, and they did sound different to my ears depending which way round they were connected. Not a huge difference I'll grant you, but it was there.