Cable screening -which end to earth

[chrisn]

Dear All

Shielded mains cables seem to have the screen connected to the 13A plug end and not the IEC female - right?

Screened signal cables have the screen earthed at the destination end. So CD to Preamp, the earth attaches to the screen at the Preamp. Preamp to Poweramp, at the Poweramp end - right?

What about power supplies and cables carrying signal and power?

My set up is -
LP12 -> P75 -> Nac82/TPX1 -> Nap140. So I can follow the above scheme for this.

I am getting some mains hum which I suspect may be caused by the earthing of the LP12 through a Lingo which is supplied through the ring main not the separatte spur which supplies the other items.

Finally what is a star earth?

Chris

 

[BobMaximus]

I assume you mean there is hum when listening to records. I also assume the LP12 is earthed via a thin black (?) cable connected to ... whatever this thin cable is connected to, remove it. Does the hum stop? If so, that's how you want to keep it.

Andy

 

[zener]

It sounds like phono stage hum , get the P75 as far away from the TPX1 and the 140 as is possible. Top shelf for the P75 , bottom shelf for the TPX/140 , if it doesn go away lift the P75 off the top shelf raise it and see what happens.

 

[Mark Packer]

Also helps to turn the P75 so it's not in the same orientation as the PSUs e.g. P75 vertical, PSUs (or other items with big transformers) horizontal.


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TPX 140

 

[zener]

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TPX1/140

 

[andyr]

Dear All

Screened signal cables have the screen earthed at the destination end. So CD to Preamp, the earth attaches to the screen at the Preamp. Preamp to Poweramp, at the Poweramp end - right?

Chris

I don't think so! My understanding is that shielded signal cables should have the shield earthed at the "lower noise" end of the cable ... which, except for phono cables, is generally the source end.

So in CD to Preamp, the screen attaches to earth at the CD.

Shielded mains cables seem to have the screen connected to the 13A plug end and not the IEC female - right?

AIUI, if a mains cable has a shield, it is there to stop (or at least reduce) radiated interference generated by the mains which is passing along the cable.

To do this, the shield has to be earthed ... and the only logical place to "earth" it is to the earth wire in the power circuit (in the wall) - which means it must be earthed at the plug end, not the component end.

What about power supplies and cables carrying signal and power?

I am getting some mains hum which I suspect may be caused by the earthing of the LP12 through a Lingo which is supplied through the ring main not the separatte spur which supplies the other items.

Good question! But what cable actually carries mains power and signal?

If you are using a shielded power cable for your Lingo, the shield should be earthed at the plug end. But this doesn't carry signal.

You may well have set up an earth loop by plugging your Lingo into a separate circuit from "the other items". Experiment - can't you use an extension cord to plug the Lingo into the same spur as the others and see if the hum goes away?

Just FYI, my Lingo is plugged into a different spur and I get no hum ... in fact, as it's a L1, my system sounds better this way as the hash which the L1 injects back into the mains is no longer buggaring up my preamp!

Regards,

Andy

 

[Mr Tweaks]

I don't think so! My understanding is that shielded signal cables should have the shield earthed at the "lower noise" end of the cable ... which, except for phono cables, is generally the source end.

So in CD to Preamp, the screen attaches to earth at the CD.



AIUI, if a mains cable has a shield, it is there to stop (or at least reduce) radiated interference generated by the mains which is passing along the cable.

To do this, the shield has to be earthed ... and the only logical place to "earth" it is to the earth wire in the power circuit (in the wall) - which means it must be earthed at the plug end, not the component end.



Good question! But what cable actually carries mains power and signal?

If you are using a shielded power cable for your Lingo, the shield should be earthed at the plug end. But this doesn't carry signal.

You may well have set up an earth loop by plugging your Lingo into a separate circuit from "the other items". Experiment - can't you use an extension cord to plug the Lingo into the same spur as the others and see if the hum goes away?

Just FYI, my Lingo is plugged into a different spur and I get no hum ... in fact, as it's a L1, my system sounds better this way as the hash which the L1 injects back into the mains is no longer buggaring up my preamp!

Regards,

Andy

I have made my own power cable with shielding. The Earth wire is indeed meant to be at the plug and whilst not attaching the shielding to the IEC end.The quality of copper is important and solid core is preferable though illegal in some countries. Just do it, the improvement is not suttle. I can advice on the best power cable materials if anyone is interested.I recommend for anyone not comfortable with making an AC cord , to buy the parts and get a qualified person to make them for you. You will still save about 300%

 

[sq225917]

Why do you think the quality of the copper makes a difference? Because you can hear a difference when you know what it's made of?

Shielding the cable might make a diffference, pretty much nothing else will as long as it can pass the current required, at least nothing that has yet been proven. and the value from shielding is from not radiating crap back into the system from your components, not from tidying up what comes in on the mains.

 

[andyr]

Why do you think the quality of the copper makes a difference? Because you can hear a difference when you know what it's made of?

Shielding the cable might make a diffference, pretty much nothing else will as long as it can pass the current required, at least nothing that has yet been proven. and the value from shielding is from not radiating crap back into the system from your components, not from tidying up what comes in on the mains.

The existence of "God" has not been proven either but Christians, Jews and Moslems believe in him!

That's a few billion people ... so if you don't, mebbe you're standing on thin ice?.

Regards,

Andy

 

[ian r]

Here we go .......

 

[Mr Tweaks]

I think the quality of any material is important through out the system.People go on about the materials used in their interconnects ( which carry low current anyway ) so why would'nt the same "quality principle" carry through to cables that carry 240v.
Single crystal copper is superior in transfering "current" than cheap copper that has impurities and kaotic molecular structure. I know what you are all thinking, am I smoking the wrong crap or what. I can honestly say that the experiements that I have done over the years have paid off and the reults are practical and relatively economical compared to the top-end ripp off Brands. Have a look at my post and click the link to see.