Dedicated mains - Survey

[Matthewjb]

@JimDog

0. Age and condition of the existing wiring
1. Separate CU and what make
2. Cable SA mm^2, and make/type
3. How many sockets of what type
4. Effect on SQ, e.g. worse, no change, slightly better, loads better, specific effects.

1. Not sure. Say 5 years when I installed it. Done around 20 years ago.

2. No just a RCD but on the side of the CU not covered by the overall RCD (ie with the fridge)

3. Not sure

4. 2 unswitched crabtree doubles. But I now only use 1 socket and a Hydra

5. Unclear. It was all done as part of moving in.

[KJC]

@Innocent_Bystander

Similarly unless the house has more than one phase supply, or an isolating transformer on part, both of which are rare, there is zero electrical isolation as such between any of the outlets on a British ring main and a separate radial circuit supplied from its own consumer unit

I thought a separate phase would help, but #2 of the 3 dedicated supplies I’ve installed in different houses was a dedicated phase and still no joy on eliminating hum. As you say IB, the ‘damage’ is usually done downstream, long before the supply enters your property. Not much we can do about that unless we want to enter the world of mains conditioning which most of us, based on traditional advice from Naim would baulk at.

[Suedkiez]

@PhilP

A thicker gauge wire has less electrical resistance and hence will convey more current over distance.

Yes, but how much? A Google search tells me:

If you take the number 19 the divide by the cross sectional area of the cable this will give you the resistance over a kilometre. (This works for copper cable)

Here are a couple of simple examples:

1, the cable has a CSA of 2.5mm²

19 ÷ by 2.5mm² will give you 7.6 ohms per km. ÷ by 1000 for resistance per meter.

2, the cable has a CSA of 4mm²

19 ÷ by 4mm² will give you 4.75 ohms per km.

So for 20 meters, the difference is 0.152 to 0.095 ohms.

[JimDog]

@Suedkiez

So for 20 meters, the difference is 0.152 to 0.095 ohms.

Yes, but we have no idea what those numbers signify in terms of how the signal will be effected (or not) as it is amplified and converted into soundwaves - will there be any difference and will it be audible or not - we do not know.

[anon33182107]

@PhilP

Pete, I meant the current rating of the wiring as I understand it - and I could be wrong - should match or be within the limits of MCB rating being used.

Phil,

Yes I see what you mean. Apologies if I misunderstood you. Not sure about the MCB rating regarding sound quality - an interesting point. When I had my 10mmsq spur it was at our previous property and was fitted around 12 years or so ago now. I honestly can’t remember the MCB rating I specified.

If I were now to fit a dedicated supply - and I won’t because at this property the upheaval would be just too much (long story!), then based on my personal experience I would specify 6mmsq cable as a mini ring circuit as opposed to a radial spur. I think I would also used screened twin and earth if I could source it. I would fit one unswitched double Crabtree socket and use a very good quality mains block.

[Suedkiez]

@JimDog

Yes, but we have no idea what those numbers signify in terms of how the signal will be effected (or not) as it is amplified and converted into soundwaves - will there be any difference and will it be audible or not - we do not know.

Well it’s a minimal difference and the resistance of the kilometers of cable upstream is unchanged. It’s just something to keep in mind while stating that “a thicker gauge wire has less electrical resistance”, despite it being literally true

[JimDog]

Yes but I think the effect on SQ of cable type in internet/signal packet systems and in electrical power systems probably adheres to something like the inverse square rule where (as long as they work) all the miles upstream have far less influence that the last couple of metres before the HiFi system.

(But please don’t ask me to prove that - I’ve only just finished work and poured a medium sized glass of cabinet Sauvignon.)

[Matthewjb]

@Suedkiez

So for 20 meters, the difference is 0.152 to 0.095 ohms.

@Suedkiez

Well it’s a minimal difference

Just looking at the numbers it’s a 30% reduction. That’s quite significant.

I’ve no idea if that translates into something you can actually hear though.

[WolF]

Hi Jim I have installed a dedicated 6mm ring main running in parallel to the meter with a single double unswitched sockets that has its own dedicated earth spike. I have then connected one 4 socket power block that all my HiFi is plugged into that also has its own dedicated earth cable to the unswithched socket. This has eliminated all amp humming noise when my ceiling fans and fridges kick in with feedback. Plus it sound a lot more musical than before. About 11 years ago, Hagar RCD unit

[RvL]

@JimDog

all the miles upstream have far less influence that the last couple of metres before the HiFi system.

Correct. Thing is, for the HiFi components it are the first couple of meters, not the last. Hence the influence of power cords that are only a meter or two.

[Suedkiez]

@JimDog

inverse square rule where (as long as they work) all the miles upstream have far less influence that the last couple of metres before the HiFi system.

That’s probably true for disturbances but isn’t resistance cumulative for the whole conductor from source to consumer

@RvL

Correct. Thing is, for the HiFi components it are the first couple of meters, not the last. Hence the influence power cords that are only a meter or two.

Resistance too?

@Matthewjb

Just looking at the numbers it’s a 30% reduction. That’s quite significant.

30% of a very small value in relation to the unchanged kilometers of upstream cable, if resistance is cumulative over the whole length (pretty sure it is)

[HappyListener]

I think we all agree that with Naim gear, especially the higher-level kit, it’s beneficial to give it access to the best quality electrical juice possible. How you achieve this in the context of your home and location could be different, and external influences play heavy here. And in the UK, the grid voltage is often identified as 240v but is generally closer to 230v now.

Personally, I appear quite fortunate with the quality of my mains if the hum of the various toroidal transformers is a proxy. In general (digits crossed), I only get to hear the Naim toroidal choir hum to itself for short periods, and when they/one does, I’m never sure why. I’m 100% convinced I’ve not got interior-house mains contamination, as events happen with no other items running…you just hear the increasing brrrrrrrr-ing.

The open question is what things like anti-surge protectors (now recommended in the UK) can do to the feed.

As for the cables and ‘draw’ capabilities, IIRC somewhere on YT there’s a vid about the output of amps and the power handling of speakers where the power delivery peaks are so much higher than the ratings of the kit.

[RvL]

Not sure I understand your question @Suedkiez ?

[Suedkiez]

@RvL

Not sure I understand your question @Suedkiez ?

In JimDog’s post that you quoted we were talking about the resistance of the last 20 meters. The resistance of one kilometer of 2.5 sqmm cable is 7.6 ohm and this is always there, probably many kilometers of it to the next power source. Then we reduce the resistance of the last (or first, if viewed from the unit) 20 meters by, say, 50% from, say, 0.15 to 0.075 ohms. In this particular case of the resistance being cumulative, I do not think that the closest couple of meter have more influence than more distant ones.

[anon33182107]

I think that focussing on resistance as an issue is probably a bit of a white elephant. Yes it is relevant, but I suggest that there are far more important issues at play that have a bearing on the musical performance of our systems. What are these factors, well RFI for one, perhaps cable microphony and no doubt others that I am unaware of.

I’ve seen the argument several times here and elsewhere that goes- what possible difference can couple of meters of specialist cable make to sound quality when the electricity is travelling through perhaps hundreds of miles of cables before that? This outlook shows a misunderstanding of the situation. As has been stated, the cables that plug into your equipment are the FIRST couple of meters that your equipment reacts to, not the last couple. These are the cables that will most influence your system - not the hundreds of miles of cabling from the power station. I’m not suggesting that these hundreds of miles of cabling do not have any effect - but we can do nothing about them so no point in worrying. Of course is one could establish where the particularly good power supplies were from power stations then I suppose one could always move house…

[RvL]

Ah… I referred to Jim’s line that all the miles upstream have far less influence than the last. I was not referring to resistance specifically.

[Suedkiez]

@anon33182107

I think that focussing on resistance as an issue is probably a bit of a white elephant. Yes it is relevant, but I suggest that there are far more important issues at play that have a bearing on the musical performance of our systems.

I can agree with that (except I doubt the small change is relevant). I was just commenting on

@PhilP

From the little I know, the wire gauge we use allows for higher levels (and ease) of electrical conductivity (current flow) to the system. A thicker gauge wire has less electrical resistance and hence will convey more current over distance.

[Suedkiez]

@RvL

Ah… I referred to Jim’s line that all the miles upstream have far less influence than the last. I was not referring to resistance specifically.

OK and I agree with that (I think )

[PhilP]

@PhilP

A thicker gauge wire has less electrical resistance and hence will convey more current over distance.

I may have been misleading and apologise when I mentioned “…more current over distance” - I had only meant this in general that a thicker gauge wire has less resistance and therefore conveys more current over any distance travelled to the components, particularly if the power amp(s) require the juice for higher listening peaks.

@JimDog

Yes, but we have no idea what those numbers signify in terms of how the signal will be effected (or not) as it is amplified and converted into soundwaves - will there be any difference and will it be audible or not - we do not know.

Agreed… From a consumer unit to the listening den in an apartment home, “over a distance” if it even reaches 20m or more - which I don’t think so unless it’s a sprawling penthouse - I really don’t think the slight differentials in resistance figures in these ohm calculations will make a sonic difference we can hear?

@Suedkiez

If you take the number 19 the divide by the cross sectional area of the cable this will give you the resistance over a kilometre. (This works for copper cable)

Here are a couple of simple examples:

1, the cable has a CSA of 2.5mm²

19 ÷ by 2.5mm² will give you 7.6 ohms per km. ÷ by 1000 for resistance per meter.

2, the cable has a CSA of 4mm²

19 ÷ by 4mm² will give you 4.75 ohms per km.

So for 20 meters, the difference is 0.152 to 0.095 ohms.

Interesting… thanks Suedkeiz… I’m always trying to simplify.

@anon33182107

I think that focussing on resistance as an issue is probably a bit of a white elephant. Yes it is relevant, but I suggest that there are far more important issues at play that have a bearing on the musical performance of our systems. What are these factors, well RFI for one, perhaps cable microphony and no doubt others that I am unaware of.

I’ve seen the argument several times here and elsewhere that goes- what possible difference can couple of meters of specialist cable make to sound quality when the electricity is travelling through perhaps hundreds of miles of cables before that? This outlook shows a misunderstanding of the situation. As has been stated, the cables that plug into your equipment are the FIRST couple of meters that your equipment reacts to, not the last couple. These are the cables that will most influence your system - not the hundreds of miles of cabling from the power station. I’m not suggesting that these hundreds of miles of cabling do not have any effect - but we can do nothing about them so no point in worrying.

Couldn’t have articulated it better, Pete.

Cheers

[Innocent_Bystander]

@Blackbird

Naim cable is 1mm2 in EU and I believe 0.75mm2 in UK

If resistance of the mains cable is a significant factor, lower being better, the Naim preference compared to, say 2.5mm cable which is still very manageable and flexible seems odd. (In terms of resistance, replacing a 1.8m long 0.75mm2 cable with 2.5mm2 would have the same effect as using 6mm2 in place of 4mm2 for a dedicated outlet cable run of 20m.)

However, I am not convinced by the resistance argument with bigger power supplies: Aside from a smoothing function, the purpose of reservoir capacitors is to provide whatever instantaneous surges in power that are needed- if they are big enough the peak capability of the mains supply surely is less critical: Picture it as a water reservoir or tank - if big enough, the drop in level with even a sudden very large short term demands (equivalent to music peaks)is negligible, and the larger the capacity the slower need be the water flow to top up, provided it can do so adequately over time. Meanwhile the top-up flow is limited by the transformer’s inductance and resistance, and ultimately the circuit breaker value rather than resistance of the cable in between.

Maybe I’m missing something, but it suggests to me that any observed audible difference between 4mm2 and 6mm2 is due to something other than resistance - the question is what?