Spur and Sockets - v - alternatives

I had a seperate spur installed in the Summer, along with new distribution board, and just had one double socket on the end of it. 6mm cable was used and MK sockets. I didn't really have room for two double sockets side by side so I now have my Hicap/140 in a Micromark multi-plug and my CDX next to it. My Linn Lingo is plugged into the normal house spur (along with a Nakamichi tape deck) as it seems to degrade the sound when plugged into the dedicated spur.
The Micromark plug seems quite widely used by other Naim owners, and does seem to be the best compromise between a socket for each box and a Multi -plug extension. I certainly have no complaints about it's performance, and it only cost about £6.99 from Maplin.

Ade

Welcome. There are many opinions here about the niceties of separate spurs. However, what everyone seems to agree on is this:

1. Any sort of separate spur is vastly better than running your system off a ring main.

2. Using the biggest "non-exotic" cable you can. In most cases, this means 30amp, 6sq. mm "cooker" cable. There are bigger ones available, but they are less easily obtainable, and difficult to handle.

3. Connection to supply:
I found the easiest thing was to connect the cable to the consumer unit terminals which are used for the incoming meter tails. With 30 amp cable there will just about be room in the terminal blocks. This connection point is about as far "upstream" as you can reasonably go, but will still involve your electician removing the big REC fuse, as the meter tails are obviously live otherwise.

4. Fusing:
Single good-quality switch box with 30a (clean) cartridge fuse. This also provides a way to isolate all the spur wiring if ever required.

5. Sockets:
Single Crabtree switched socket. You can plug your existing extension block into this, and it also provides a good match with MusicWorks extension blocks if you ever want to upgrade.

All this I think provides a lot of potential improvement, using stuff which your electrician will find easy to obtain and doesn't cost too much.

Best;

Mark

(an imperfect
forum environment is
better than none)

Think very carefully about where you site the sockets. I wish I had arranged mine differently now. My next house will have plenty of them all over the place to allow for maximum flexibility.
Cheers
Steve

If there is no current flowing in the ground leads then how you arrange them - serially/star - and the thickness of the wire and so on shouldn't matter. I believe starring is used to prevent simultaneous currents in a shared resistive conductor from creating an additive voltage drop.

So I have a couple of questions: 1) how big was the performance impact of your special grounding arrangement and 2) are you aware of current flows in the ground lines during normal operation and if so what do you think causes them? 3) Is there some other effect that I'm missing?

BAM

I believe the manly amperage rating is actually for decreasing resistance created by the breaker.

A busty 50 amp boy,

dave

Why?

I mean,err, I personally wouldn't want my mains earth lead getting anywhere near my signals. It's necessary for safety reasons to earth the metal boxes, but what's it got to do with the audio signals?
BAM

But provided your earth connects to 0v at a single point I don't see how current can flow in the earth line. Where's the circuit?

If there is no circuit then who cares what the earth wiring back to the fuse box is like and who needs a 100ft solid gold rod driven into their back yard?

BAM

Why does it matter? The main reason is that you are trying to provide 0V EXACTLY at the equipment. The best way of doing this is couple the equipment directly to the earth (perhaps we should all be siting our amps outside to get the circuit as close to ground as possible don't try this at home... )

Wire has a small but finite resistance which leads to the earth end being at exactly 0V but the other end (which attaches to your equipment) "seeing" earth through the finite resistance. This resistance allows the equipment end to be not quite at 0V. All you are trying to do with big cables is reduce the effect of this resistance as the bigger cables have lower resistance for a given unit length).

Remember, the values involved are all relatively small (being fractions of an ohm for all sensible lengths of cable) but they are finite and do contribute to degredation.

Hope that helps.

Andy

From what I can tell, Naim uses the ground from your house for safety purposes, and I don't believe that any current ever flows in that direction. Therefore, I don't know why it would make a difference if the ground connection were better.

I should mention, though, that I'm in North America, so maybe it's different here. I've also not traced the actual signal path in the electronics. Regardless, it would be very odd if Naim were routinely shunting current out the ground wire. This sounds like a rather dangerous concept, and I'm pretty sure that it's not happening.

-=> Mike Hanson <=-

in an non-"balanced" design like Naim, the +ve signal wire carry the signal, and the 0V (common throughout all the boxes) provides a reference against which that signal is measured. The Signals have not meaning, except in relation to that 0V.

Naim ties the 0V of the system to mains earth in either the CD player or record deck. A very low resitance connection to earth with then provide a more stable signal reference, which will improve sound quality.

cheers, Martin

enjoy...

ken

That's absolutely right. The absolute voltage of the common ground is irrelevent: electrons care about voltage differences only. Furthermore there is no circuit formed by the mains earth - except at radio frequencies, you need a circuit for current to flow - ie: a loop with a voltage gradient along it.

The term signal reference sounds like an absolute thing because of other ways in which we use the word reference. But as far as electrons are concerned there are no absolutes, so whenever someone mentions a voltage reference they really mean a relative voltage reference. It's not like temperature where you can say something is at 55 Kelvin and that has absolute meaning. Voltage is merely a difference measurement. Only current is absolute.

So, if you have no circuit you will have no relative voltage difference and no current. If there is no current path then there is no impedance by definition.

So having stated the theory, has anyone got listening evidence that changing your mains ground wiring (assuming a single point of connection to your system) makes any significant difference?

BAM

enjoy...

ken

I believe that floating the ground part of the circuit in a Naim system will leave it very susceptible to RF interference.

Naim kit does not like RF.

BAM,

Yes, the “ground” is just an arbitrary voltage. Think of it like a huge capacitor. If it’s massive enough then you could put substantial amounts of current into it with absolutely negligible changes in the voltage (since the charges are distributed over a very wide area).

If you have an earth spike down into the water table, then I suppose that “capacitor” could be several miles across & weighing thousands or millions of tons.

Think of the earth like the foundations of a house. It provides a stable reference for everything else to be built on.

cheers, Martin

Electricity and mechanics are quite different in this respect. Electricity needs a circuit. I think you, and others, are falling into a common trap of treating one like the other. Terms like "stable foundation" are mechanical terms. Also, your assertion that RF immunity is increased by grounding the circuit to earth is not correct. You have to be careful not to mix up concepts. It's easy to do.

If anyone would like me to explain this in more detail I would be very happy to do so.

I offer my contributions to this thread in the interests of saving people hundreds of pounds/dollars having an electrician rewire their mains grounds due to mis-information about basic physics. I also want to save people worrying needlessly about this.

BAM

[This message was edited by bam on SUNDAY 11 February 2001 at 17:48.]

quote:

---

If anyone would like me to explain this in more detail I would be very happy to do so.

---

i would like to see your explanation.

i had serious RF problems sometime ago, which was very evident with the phono input active -- and this was with my equipment grounded properly. i actually didnt know that floating your naim equipment would make it more succeptible to RF --i thought in fact its improper earthing that may exacerbate RF interfererence -- i am no expert. i know for sure that floating may make certain equipment unsafe.

are speakers earthed by the way?? i see only 2 wires going there from the power amp...

enjoy...

ken

Actually, I don’t think so.

As with any system not in equilibrium, current will always flow from a higher to a lower Potential, if there is a path for it to do so.

That current will continue to flow until the Potential Difference has been reduced to zero. In a normal circuit the charge holding capacity of the wires and other components (except power supply capacitors) is negligible, so any P.D. differences will be evened out in a tiny fraction of a second. Once this equilibrium is achieved, *then* no current will flow.

In the case of a well-installed earth spike, the charge-holding capacity of that portion of the Earth’s crust which is in electrical contact with the spike is very large. When the amp is connected to that spike, charges will be transferred (i.e. current will flow) until equilibrium is reached. This will take place more quickly if the path to the spike, and the spike’s connection to the ground are both low resistance.

Electrically, there is a circuit *within* the Naim amplification system, with the 0V line providing the return path. However, the circuit also relies on that 0V line being tied to earth at some point (either internally in the CD player, or at the earth binding post on the LP input). My understanding is that this is to ensure that the currents flowing through the earth path do not cause a modulation of the voltage of the 0V line (it wouldn’t then be 0V!) as the positive part of the signal only has meaning when referenced against a * stable * 0V.

The stability of that 0V will be improved by a lower-impedance path to earth

cheers, Martin

P.S. When the power company distributes electricity on high voltage lines, the return path is through the ground. However, this is not how the ‘Ground’ works in this context.

Ok.

"This will take place more quickly if the path to the spike, and the spike’s connection to the ground are both low resistance."

Ok - so this will now happen in a tinier, tiny fraction of a second. So differences in static charge go away - how is this relevant?

"However, the circuit also relies on that 0V line being tied to earth at some point"

No. This is not correct.

"My understanding is that this is to ensure that the currents flowing through the earth path do not cause a modulation of the voltage of the 0V line (it wouldn’t then be 0V!) as the positive part of the signal only has meaning when referenced against a * stable * 0V."

No. This is not correct either. Again, "0V" is a relative reference and 0 is just used for convenience. It could be called xV if you wanted. The positive supply voltage is simply the difference between the pos and xV; the pos=x+24 say. But it doesn't matter what x is.

If you ran your Naim off batteries with no external earth connection it would work just fine in this regard. How does all the electronics in an airplane continue to work without a "stable" ground? Will astronauts in space never be able to enjoy good hifi?

BAM
Batteries...hmm. There's an idea: low resistance, no mains noise, no 50/60Hz noise or regulator switching noise. Anyone tried this?

I assume that the earth wiring in most houses is carrying rubbish from the fridge, TV, computers etc which doesn't do much good to your naim gear.

A separate earth line surely helps reduce this.

Battery PSUs have been discussed here several times. I recall JV writing that he found them less good for various technical reasons. I think forum member Pete Maddex tried batteries without much success.

Jo

Topics such as this used to get useful responses from Julian that gave fascinating insights into the whys and hows of naim gear.

Is it not possible for Roy or one of the other technical guys to do this?

Thanks.

Jo

I suspect that the improvements to be had from better local earthing of the system are largely from improved screening and reduced noise.

Whilst your assertion that the absolute potential of the (signal) 0V is not entirely relevant is correct when viewed at D.C., at any frequency above this it is not true.

quote:

---

"This will take place more quickly if the path to the spike, and the spike’s connection to the ground are both low resistance."

Ok - so this will now happen in a tinier, tiny fraction of a second. So differences in static charge go away - how is this relevant?

---

This is relevant because this could be happening millions of times a second if there is any RF around. Think beyond static charges and things change.

Naim systems use star earthing, referencing all signals to the signal 0V present within the power supplies. The absolute potential of this point, relative to a theoretical 'absolute' ground is not relevant, but if the entire system was allowed to float with respect to our absolute ground (which in this case is our local mains earth) this does bring problems.

At any frequency above DC we cannot assume that the electronics will work satisfactorily against a rapidly changing reference voltage.

If RF is introduced onto the signal 0V (and there's plenty of it about) you are assuming that the circuitry will be unaffected by this, which I can categorically guarantee is not the case.

The RF signals will not be present on all areas of the circuitry at the same levels, at the same point in time. They will induce current flows within the circuitry, they may overload sections of analogue elecronics causing it to behave in a non-linear fashion, and in the worst case may even be demodulated (RF breakthrough).

Tying the system, at a single point only, to a good local earth will reduce the amplitude of the interfering signals, and is likely to improve performance of the circuitry. The internal bandwidth of Naim equipment is high, and it could be amplifyings signal you cannot hear, consuming power and affecting audible signals. Reducing this efect is likely to bring benefits.

Martin's statement is therefore correct when you consider the earth as a large capacitor. It will effectively decouple RF signals from the system as a whole. It is my belief that the best benefits are obtained from a local earth with a low impedance acros the widest possible bandwidth - a very difficult thing to acheive once one starts to consider the earth wire as a transmission line!

The key to al of this is to remember that once one rises above DC things behave very differently .

quote:

---

Batteries...hmm. There's an idea: low resistance, no mains noise, no 50/60Hz noise or regulator switching noise. Anyone tried this?

---

Yep - Naim have. Low bandwidth and step-delayed voltage changes from the chemical reaction response within the cell lead them to believe these were undesirable attributes in an audio PSU.

Andy.

Andrew L. Weekes
alweekes@audiophile.com

You just save me from having to write 'exactly' the same thing. Were we separated at birth? I used to live in Bromley, Kent... just up the road from you!

Best Regards,
Mark Dunn

Re:

>Just before I get engrossed in HF/RF field theory >(I feel a Faraday cage coming on)

I moved house about two months ago and in my old residence I actually built a Faraday cage around my 102 (because RF was too intrusive) with excellent results. Just one more advantage of a remote controlled preamp ;-)

>Are you implying that Naim equipment will be more >susceptible to RF fields and
>conducted noise in space than it will when it's
>0v network is connected to mother earth through a >few metres of wire?

If my memory serves, Gaussian theory predicts that the probability that the average value of an EM field in *finite* space will be zero, is very low. So the answer to your question is most probably 'yes'. It's easy to test the assumptions, - simply float your system earth and/or turntable ground and listen. I've done it and the difference is immediately audible.

Best Regards,
Mark Dunn
È