Noise and DC on mains and new radial

I'm not attributing RFI to my transformer hum, Huge. (I was going to put in a BPS to handle any DC, which I hoped would handle the hum; but I've actually cancelled that and decided to be patient and go one step at a time. See what the radial does and add a BPS into the radial, later, if necessary.) I'm simply concerned to make the best of the radial job. I don't know if I suffer from RFI but it seems logical to effect the job in such a way that, if it is present, I don't undo all the good of the dedicated socket by siting it in the wrong place.

I take pictures; I don't do radio interference - hence why I'm asking the question! I didn't say a Powerline wasn't expensive - my reference was 'in the scheme of things' - i.e. it was comparative. If you've spent £30k on your entire system over the years, another £500 is less than 2% of that cost. Seems pretty reasonable for a clean power supply (which is far more reaching than a Powerline) and all that it's reputed to bring. 

The transformer hum / RFI comment was in response to Ian's post.

OK I have a little more time now...

In terms of RFI jumping from cable to cable, approximately speaking, the coupling is inversely proportional to the square of the separation but directly proportional to the length*.

So a short length where the cables are in close proximity will have little effect.  If the cables cross at 90°, then there will be very little coupling at all, even if the outer jackets are actually touching.  The biggest thing to avoid would be running both cables within the same metal conduit.  However from the RF perspective if one or other cable is in a separately earthed metal conduit (N.B. the quality of the earth is specifically important here, so it's not a simple as it appears!) then they can be close with no problems.

* This is also dependent on frequency where the length starts to approach 1/10 of the wavelength of EM waves in air at that frequency.

That is hugely helpful, Huge! Many thanks and we'll make our plan accordingly. 

@huge - Good answer there....  

[@mention:26908937791111692] - Agree with [@mention:36201736971392588] that the transformer audible hum is not due to RFI. Believe its more due to harmonics (or 'noise') on the incoming mains supply - which the separate spur ought to help with. BUT - it depends whats causing the harmonics......!  If you can identify the source - and fix it, thats best. 

Thanks. But, just to be clear, I never said the hum was caused by RFI RFI came to me as an after-thought in relation to how we should consider the proximity of radial and ring cables to each other when running the radial.

The hum may be caused by DC and if it's there on the radial and it bugs me, I might add the BPS; though I don't know how that will affect SQ dynamics, given it may increase impedance. (According to Naim tech support.) 

If you're worried about it, you could always ask your electrician to run the cable in a suitable shielded trunking. It can be a bit of a faff to instal compared to just T&E cable.

I worry about everything Chris. Thanks for that. Will discuss with sparks over weekend. 

ianrobertm posted:

@huge - Good answer there....  

[@mention:26908937791111692] - Agree with [@mention:36201736971392588] that the transformer audible hum is not due to RFI. Believe its more due to harmonics (or 'noise') on the incoming mains supply - which the separate spur ought to help with. BUT - it depends whats causing the harmonics......!  If you can identify the source - and fix it, thats best. 

Harmonics - well sort of!

Zero order harmonic (+ even order harmonics):  In other words it's usually an asymmetric mains waveform, where one half cycle is attenuated relative to the other.

This is most often referred to as a DC offset (actually, not quite the same thing, but similar enough to pass muster and same technical fixes apply).

The configuration my sparks is, as I write, putting in, is the recommended separate CSU off the mains tails with a 32A Type C RCBO and 10mm2 cable to twin MK wall socket, TT earthed to a spike. He's told me that there is no reason why this dedicated radial can't be earthed TT, even though the rest of the house and its CSU is on PME.  (Separately, my mains were upgraded last year and are now running a 100amp fuse.) If any (qualified) person thinks he's an imposter pretending to be an electrician with this plan, I'd be grateful for a flag. Thanks.   

..to be more precise, the mains tails come off the meter, then through an isolator; the radial is being taken off the tails after the isolator..

eagle3333 posted:

He's told me that there is no reason why this dedicated radial can't be earthed TT, even though the rest of the house and its CSU is on PME.  (Separately, my mains were upgraded last year and are now running a 100amp fuse.) If any (qualified) person thinks he's an imposter pretending to be an electrician with this plan, I'd be grateful for a flag. Thanks.   

My sparks says the same, as did all the other sources, with whom I double checked after concerns were raised earlier in the thread.

Keith

You should have physical separation between the two earth zones so you can't accidentally 'short' across the two earth zones by a person and any equipment or conductive surface between the two (shielded Ethernet leads come to mind). .. if in doubt talk to a commercial electrical contracting consultant (as opposed to a sparky).... I did recently to double check on the advice had been given by the RSGB. At least you need to be aware of the very low probability but potentially fatal risks you are taking. An electrician may well  wire this for you as they will assume you are aware of the risks.... it's not a regulation thing... it wasn't last time  I looked anyway...

Perhaps an audiophile slant on this might help some understand..

http://www.acoustica.org.uk/t/earth.html

Hi Simon

The possibility was discussed with the electrician and several others, but as you say, it is very unlikely. Unlikely, as in zombie apocalypse, to quote one of the experts to whom I spoke.

Hmm, according to RSGB it happens, so not that rare... their members are perhaps  more inclined to do this than the typical audiophile however.. I don't believe there has been a fatality but there have been shocks and equipment damage, So it's a case of real feedback of affected users or those who think it might not happen. The RSGB has now created a special safety leaflet for PME installations where separate earth electrodes may be used for antenna installations and locally earthed equipment  for its membership and their safety  ... alas there is no equivalent for the budding audiophile.... of course if your primary house supply is TT then having a separate earthed radial is fine ... it's only the PME installations where issues may occur with the potentially large difference in earth potentials.. and not just in fault conditions.

For the record I did experience a shock when I first set a local electrode with PME supply... I got quite a buzz and it frightened me as I was concerned not just for me but also my then very young children. it was then I looked into it.. my house is now fully TT and I have a certified electrode, as well as  my own electrodes... no issues ever since... and nuisance tripping has declined as well.

Thanks for the feedback, Simon. I asked my sparks about the danger of shorting across the two earth zones and whether there was anything I could do, in the normal course of events, which could cause that to happen. His reply was no and that we have a completely safe set up. I hope he's right.

Meantime, the reading at the spike was 130ohms so he's going to sink another, longer spike about 8 metres from the first and join them. 

After a 30 minute evaluation I have to report a disappointing result. Soundstage width and depth is shrunken; warmth and bass greatly reduced; compressed hard edged sound. Dreadful. Plug back into the main ring and harmony restored. Definitely not what was expected. Any thoughts anyone? I remember reading a thread where someone posted the same experience but I discounted it amidst an ocean of positive results. There must be a logical answer..  

Good to hear... and it probably means your  metal switch light fittings and radiators are well away from your independently earthed devices... if your electrician has stated this on the certificate and no special provisions are required, brilliant... keep a safe copy of it.

Yes sinking multiple longer electrodes to reduce earth electrode impedance to below 100 ohms is good practice,.. although upto 200 ohms is valid currently apparently

Sorry Simon, perhaps I wasn't clear. The sound is dreadful on the new radial, not the main ring!

eagle3333 posted:

After a 30 minute evaluation I have to report a disappointing result. Soundstage width and depth is shrunken; warmth and bass greatly reduced; compressed hard edged sound. Dreadful. Plug back into the main ring and harmony restored. Definitely not what was expected. Any thoughts anyone? I remember reading a thread where someone posted the same experience but I discounted it amidst an ocean of positive results. There must be a logical answer..  

Oh dear that sounds frustrating ... did you hear the radial with the PME earth, so do you know whether it's the radial  wiring and RCD that is causing this or your local earth.... I do think the latter is unlikely, but the former probable... 

Assume you only have your Naim plugged into this radial, and you have thick juicy copper wiring in your radial?

Nope, but that'll be the line of enquiry, so to speak. Thanks, Simon.

He's back on Friday to fit my type C MCB instead of the type B he brought - yes, the amp trips it.. Hopefully he can try it with the PME earth without too much trouble. The difference is night and day - but in the wrong direction!

Yes - just the amp, pre', dac and ndx plugged into the socket via hydra..

He used an MK RCD and MCB. 

Ok something sounds wrong... do report back when you have spoken with your electrician...

Will do. The instal' is incredibly neat and professional looking, FWIW. I'd post a picture but I have nowhere to host it..

Simon, could this be the effect if the 10mm2 cable wasn't properly attached in the socket?

Yes it could indeed - do you have your doubts?