Shielded cable use...

[user 6351]

Need some advice please (or just general thoughts for now...).

Customer is a little bit music obsessed and when I recently did a CU replacement for him, he specified a dedicated circuit just for his music kit.

This was a separate way on the board with a 20A RCBO; 4mm shielded cable 3 core (braided copper shield which was then earthed at the CU) supplying 1 socket outlet.

Now... the way I understood it was that the 3 cores would do everything I needed with regard to supply and earthing arrangements and the shielding would help with any noise problems.

However, he has now come back to me as he has had some differing opinions from other music fans, some of which suggest that this could damage his equipment.

Does anyone have any experience in this area??

Thanks,

Ian.

 

[batty]

Another one fooled by idiots that sell stuff and make them think they hear things different to the rest of us. Just disconnect the braiding before the consumer unit if thats what he wants.

 

[kme]

Right!

The theoretical idea is twofold:

1. The braided sheath stops noise & interference being picked up by the cable (same as coax)

2. The individuated supply avoids "earth loops", which can create hum.

If you`ve terminated the braid at both ends; AND terminated the earth core at both ends, you`ve essentially created an earth loop. What this may do is generate hum - this isn`t male cow poo, this is fact.

What it will NOT do is damage his equipment, FFS - whoever said that is talking out of their rear end, TBH.

Drop the braid at the socket end - leave it connected at the CU - loop removed, hum minimised.

KME

 

[Sidewinder]

^+1 to KME

 

[steptoe]

Im with KME, that is how we connect the beldon cable on the heat pumps for the programmer, shield connected at one end only.

 

[fletchflash]

I have a few bits of music gear, its called "ground loop interferance" and it can be quite a loud buzz.

Some DIY type musicians end up dissconnecting earths from circuits, and ive heard of music gear exposed parts coming live. Guitar strings then touching microphones, really dangerous.

 

[user 6351]

Thanks guys.

I probably should have gone a bit further in my OP when I said that I had connected the braid in the CU, I should have explained further that I isolated it at the socket end as well, so my installation is as per KME's post.

It's nice to know that I was right in the first place, as when he put it to me the other day, I couldn't for the life of me think of anything wrong!!

BTW, the chap in question is a sound engineer by trade, so I do allow him a bit of leeway for wanting a posh set-up!! (although when he demonstrated it to me I couldn't tell any difference with my normal mortal hearing!)

Thanks again everyone.

 

[steptoe]

Remember to line the slots on the screws up in the horizontal plane!

:slap

 

[kerching]

Customer of mine years ago was a Musico. Dedicated music room built with no wall junctions at rightangles to another, even had a slope to roof and walls built out of plum to eliminate toatal internal reflection. Loud speakers that needed a 240v supply to them. Speakers had to be 1 metre out from wall.

And to be perfectly honest the difference that it made was frick-all [and his taste in music was cr4p as well].......he reckoned that it changed the 'coloration' of the Music so, I agreed and he was impressed.......tell them what they want to hear............... :coat

 

[kme]

Electrostatic speakers - They ARE awesome mind..........

I used to have a Quad

You can clearly see the segregation internally between the drivers: one treble panel centrally, with a pair of bass units alongside. The guy has two `cos they`re only mono.

The internal voltage to the drivers is up to 6KV - the sound is phenomenal. My Father worked with the guy who designed `em - my audiophile "claim to fame".

n.b. I also used to do sound engineering -

and yes, you DO put them away from a wall - at least a metre.

FYI: St. Georges hall in Bradford had a demontration of them, circa 1970.

ONE of these speakers, driven by a Quad 22 Valve amp (15W RMS output) - easily filled the auditorium with sound.............

 

[Curley]

My two cents,

jabzuki stated three core screened more than likely the third cable would be connected to earth KME is right on the theory side, just the wrong conductor, as we heard late that the screen was only grounded at one end, as it should be.

I served my time repairing top end audiophile (silent p) kit, spending my time tweaking for people with far to much money, anyhoo taking for granted that the kit isnt double insulated and that your audio chappy is using good quality (batty money) leads of fiber interconnects the way to go would be an isolation transformer on the supply and if hes still not happy a notch filter on the pre-amp output, (people will tell you that human hearing is 20Hz to 20kHz, yeah it is until you hit puberty,or goto your first gig etc)

If he's a real nerd he may have a pure class A power amp, now if he has then message me back for more tricks.

ow yeah and just in case hes old get him to change the battery in his hearing aid

Good luck

 

[kme]

Exsqueeze me?

Without going back to verify.....................

no, wait.................

Right - checked. We DID cover the 3 core screened cable; I don`t know how you managed to misread a reference to "the wrong conductor" mate?

I would expect the customer to have that side of it covered; there`s no point the O/P trying to educate the end user in all variants of noise reduction - as you`ll be well aware, it can be a very "tweaky" business

I used to use my own custom interconnects, which ALSO dropped the earth at one end - meant you could safely remove earth loops without disconnecting the earth wire in the plug (used to be a common solution to problems with valve gear)

KME

 

[user 6351]

Well, bearing in mind that I am more than happy with my music on the iPod at a moderate bit rate, then just stuck in a docking station if I need speakers, you can probably tell how fussed I am about the quality of my music!! I can't tell the difference between a

 

[kerching]

My two cents,jabzuki stated three core screened more than likely the third cable would be connected to earth KME is right on the theory side, just the wrong conductor, as we heard late that the screen was only grounded at one end, as it should be.

I served my time repairing top end audiophile (silent p) kit, spending my time tweaking for people with far to much money, anyhoo taking for granted that the kit isnt double insulated and that your audio chappy is using good quality (batty money) leads of fiber interconnects the way to go would be an isolation transformer on the supply and if hes still not happy a notch filter on the pre-amp output, (people will tell you that human hearing is 20Hz to 20kHz, yeah it is until you hit puberty,or goto your first gig etc)

If he's a real nerd he may have a pure class A power amp, now if he has then message me back for more tricks.

ow yeah and just in case hes old get him to change the battery in his hearing aid

Good luck

Yeah thats what I thought, Notch Filter. Can't have enough Notch Filters, never never enough Notch filters. Wuffle valves, their not to be sniffed at along with Dibbits and Kimpfs...........Sorry, ranting sarcastically again. Been a really bad week AND it's only Tuesday.

Hey Ho, it's only money after all............... :coat

 

[kme]

Sounds like we`re sharing the same bubble bath, matey :slap

.......What`s "only money"?????.........I`se forgotten!!!

Ne`er mind - just been authorised an 8-day PIR - that`ll keep the wolf at bay for another week or so.........................