Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems Getting the best sound... power conditioning

Thanks Mirek - much appreciated.

Very interesting stuff!

Chenko, can I ask how the three phase supply is converted in the house back to 240V for both the AV feeds and the rest of the house ring circuits? Given the blank looks I faced when explaining star earthing and dedicated spikes to our electricians, I forsee huge problems in being able to direct a jobbing sparkie through such a task!

Cheers

George

I'm accompanying an electrician (who's au fait with commercial A/V installations) to my new place on Friday. I'll report back on what I learn from that!

I suspect that one phase is used for the house and another phase for the HiFi.

Voltage phase to earth is 240v
Voltage phase to phase is 415v

Each phase's sinewave is 120 aways from the others.

If you have single phase outlets (240v) in the same room (might even be floor or house?) that are fed from different phases you need to label all the outlets, with phase / 415 volt warning notice.
As the (fatal) potential across phases is 415v (phase A - live to phase B live).

Regards,
Carl.

Bad weather has delayed my "AV-familiar" electrician from inspecting and advising. Hopefully he'll do so sometime soon.

don't need 3 phase for hifi
thats for industry
just sep spur
excellent ground
breaker box
fuses on live side
sensible plugs and sockets with shutters and insulated prongs
then faff with silly power condition etc.
roger

Riddle me this. How does 415v become 240v? Here in the US, 240v from the pole become 2 x 120v at the breaker box.

Frank, I found this online:

http://mysite.du.edu/~jcalvert/tech/wyedelta.gif

Most alternating-current (AC) generation and transmission, and a good part of use, take place through three-phase circuits. If you want to understand electric power, you must know something about three-phase. It is rather simple if you go at it the right way, though it has a reputation for difficulty.
Phase is a frequently-used term around AC. The word comes from Greek fasis, "appearance," from fanein, "to appear." It originally referred to the eternally regular changing appearance of the moon through each month, and then was applied to the periodic changes of some quantity, such as the voltage in an AC circuit. Electrical phase is measured in degrees, with 360� corresponding to a complete cycle. A sinusoidal voltage is proportional to the cosine or sine of the phase.
Three-phase, abbreviated 3φ, refers to three voltages or currents that that differ by a third of a cycle, or 120 electrical degrees, from each other. They go through their maxima in a regular order, called the phase sequence. The three phases could be supplied over six wires, with two wires reserved for the exclusive use of each phase. However, they are generally supplied over only three wires, and the phase or line voltages are the voltages between the three possible pairs of wires. The phase or line currents are the currents in each wire. Voltages and currents are usually expressed as rms or effective values, as in single-phase analysis.
When you connect a load to the three wires, it should be done in such a way that it does not destroy the symmetry. This means that you need three equal loads connected across the three pairs of wires. This looks like an equilateral triangle, or delta, and is called a delta load. Another symmetrical connection would result if you connected one side of each load together, and then the three other ends to the three wires. This looks like a Y, and is called a wye load. These are the only possibilities for a symmetrical load. The center of the Y connection is, in a way, equidistant from each of the three line voltages, and will remain at a constant potential. It is called the neutral, and may be furnished along with the three phase voltages. The benefits of three-phase are realized best for such a symmetrical connection, which is called balanced. If the load is not balanced, the problem is a complicated one one whose solution gives little insight, just numbers. Such problems are best left to computer circuit analysis. Three-phase systems that are roughly balanced (the practical case) can be analyzed profitably by a method called symmetrical components. Here, let us consider only balanced three-phase circuits, which are the most important anyway.
The key to understanding three-phase is to understand the phasor diagram for the voltages or currents. In the diagram at the above, a, b and c represent the three lines, and o represents the neutral. The red phasors are the line or delta voltages, the voltages between the wires. The blue phasors are the wye voltages, the voltages to neutral. They correspond to the two different ways a symmetrical load can be connected. The vectors can be imagined rotating anticlockwise with time with angular velocity ω = 2πf, their projections on the horizontal axis representing the voltages as functions of time. Note how the subscripts on the V's give the points between which the voltage is measured, and the sign of the voltage. Vab is the voltage at point a relative to point b, for example. The same phasor diagram holds for the currents. In this case, the line currents are the blue vectors, and the red vectors are the currents through a delta load. The blue and red vectors differ in phase by 30�, and in magnitude by a factor of √3, as is marked in the diagram.
Suppose we want to take two phase wires and neutral to make a three-wire household service supplying 120 V between each hot wire and ground. The neutral will become the grounded conductor, the two phases the hot conductors. Then, the wye voltage is 120, so the delta voltage will be √3 x 120 = 208 V. This is the three-phase line voltage necessary in this case. Note that the two 120 V sources are not opposite in phase, and will not give 240 V between them. On the other hand, suppose we do want a 240 V service. Then this must be the line voltage, and the voltages to neutral will be 139 V, not 120 V. A 120 V three-phase service will give only 69 V from line to neutral. Note that √3 appears everywhere, and that the differences in phase explain the unexpected results.

In Germany and Switzerland, where three-phase power was originated and developed, it is known as Drehstrom, "rotating current" for this property of constant power. Ordinary AC is called Wechselstrom, or "change current." Nikola Tesla, the discoverer of polyphase currents and inventor of the induction motor, employed two-phase current, where the phase difference is 90�. This also can be used to create a rotating magnetic field, and is more efficient than single-phase, but is not quite as advantageous as three-phase. Two-phase power was once rather common in the United States, where Tesla was important in the introduction of AC, but has now gone completely out of use.
Two-phase can be supplied over three wires, but there is no true neutral, since the phases are not symmetrical. However, it is always easy to double the number of phases in a transformer secondary by making two secondary windings and connecting them in opposing phases. Four-phase does have a neutral, like three-phase, but requires four wires. In fact, three-phase is more economical than any other number of phases. For applications like rectifiers and synchronous converters where DC is produced, it is most efficient to use six-phase AC input, which is easily produced from three-phase in a transformer.
If you are transmitting a certain amount of power single-phase, adding one more conductor operated at the same line voltage and current and using three-phase will increase the power transmitted by 72% with only a 50% increase in the amount of copper and losses. The advantage is obvious. Under certain conditions, transmitting a certain amount of power by three-phase only requires 75% of the copper of single-phase transmission. This is not the major advantage of three-phase, but it does play a factor.
Three wires are usually seen in high-voltage transmission lines, whether on towers or poles, with pin or suspension insulators. Some high-voltage lines are now DC, since solid state devices make it easier to convert to and from AC. The DC lines are free of the problems created by phase, as well as eliminating the skin effect that reduces the effective area of the conductors. It is not nearly as easy to manage long-distance electrical transmission as might be thought.

Thanks folks. Sorry for being off-line for a few days - I've been at my new place with a builder's (hard) hat on.

The new feedback is most appreciated. On Friday, my recommended electrician turned up for a site visit. But, while he's AV-familiar, he didn't add anything to my knowledge and was "behind the curve" viz-a-vis the discussions we're having here.

Chenko, wow! I've learnt some more - and got more confused at the same time!

Roger, that checklist is really helpful - thanks. I was thinking things through just now - which spurred (excuse the pun) me on to get back to Hitchhikers. Could you please elaborate:

1) don't need 3 phase for hifi; thats for industry

OK. My new place happens to have it. Is that neutral or detrimental compared to single phase?

2) excellent ground

Yes, I see this as a pre-requisite. I'll get the qualty of earth tested and, if need be, add an external ground rod.

3) sensible plugs and sockets with shutters and insulated prongs

Yes, I'm sold on Neutrik for this.

4) then faff with silly power condition etc.

I've heard the arguments that these can add problems as well as cure them and am not convinced. Moreover, as I have a three phase supply, I believe I have a nice stable supply which doesn't need conditioning.

5) just sep spur

Yes, I see the need for this in principle. But I'm hazy on the specifics. I plan to dedicate one of the three phases to AV and for this to supply:

� a TV room (screen + TV box);

� a home cinema (5.1 DSP speakers + a rack of gear); and

� a music room (2 DSP speakers plus a rack of gear).

Is it sufficient to have a single supply which is then split to feed all of the above? Or a spur to feed each room? Or a spur to feed each speaker pair and each rack? Or to feed each individual speaker and each rack?!

6) breaker box

I understand the safety need for this. Does it add any other value?

7) fuses on live side

Isn't fusing always on the live? Sorry if I'm missing something here.

All the best,

If you are thinking of using Neutrik PowerCon type connectors, please be aware they are not designed to be either inserted or removed whilst the power is switched on.

Other than that, I can highly recommend Neutrik.

Steve.

Sounds like they won't meet building regs or 18th edition wiring regs. Obviously you can swap them after inspection but this may have other implications.

I don't know much about 3 phase but ...
1 doesn't the load on each phase need to be approximately balanced? If you put your hifi one one phase and rest of the house on the other it doesn't sound like it's going to be particularly well balanced.

2 you may share some phases with 'industrial' installations that run heavy machinery and thus have a more polluted supply in the first place. When the road and surrounding area that my wifes school totally lost all it's power her school only lost half it's power; the side that was shared with the domestic load. The other half was unaffected as its shared load was outside the affected surrounding area but possibly with the nearby industrial complexes.

Hello Andy,


Iam in a similar situation, as my listening room needs to be finished.
I have a previsional installation.
Iam just testing different power cables and the PS audio premier conditioner.
Also i can choose how many phases i want to use.
Here in Austria every house have 3 hot(phases) and one neutral that get delivered by the power company.For flats the phases are most times fixed-no choices can made..

The electrician makes at the house a local earth connection(digg and burried a solid wire in the earth).
At the entry of the power in your house-ONLY at one point- the NEUTRAL phase get connected with the earth(this is also for safety)
The voltage between neutral and phase is 230 VAC and between phases ist 380 Volt(230 * squareroot of 3)
The choice what phase you are using and for which purposes can be made and changed without big problems.

So you can decide to use one phase for hifi-the other for the "standard things".
Or you distribute your stuff on all 3 phases.
To select one phase for hifi have the advantage that your "other" stuff in the house doesnt disturbe your hifi equipment.
Choicing three phases is better in "current time distribution".That means when you have heavy amps with one phase all amps surge the current when the sinus shape voltage have the maximum.
This "flaten" a little the peak and can cause distortions.
With 3 phases the maximum of the voltage is shifted in phase(120 degree), that means the current doesnt "surge" at the same time on all amps and also have less load for each phase.
And that means the peak get less disturbed as on one phase.

IAN, practically the balance issue of the loads on all 3 phases is not very sensitive as long you dont kWatts of power ;-))
Of coarse, one major point to select a specific phase or choose 3 phases is the quality.
You have to look with an oscilliscope or a suitable THD meter on the phase.
If one phase is badly, the decision for 3 pahses its not a good choice.
If you choose one phase,you should select the pahse with the lowest distortions.
The problem is her that you have to watch it multiple times, because the distortions always changing over the day and night.
And which kind distortion is more or less important for your equipment, its a question where only your experiences and hearing results can brings the "fact".

Thats not easy, but when you have 3 phases at all, you can try them at different times to hear whats the best for you.
The disturbances of the equipment themselves and to each other is also a point for your decision one or 3 phases as explained above.

And this variess with the power cable and filter or conditioner.
So Iam personally will go the way with one phase, but its not finalized yet.

I tested the PS Audio premier on the source, the sound get "cleaner" but more "harder".
So i have to put the "DUETT" a filter in front of it-thats changed a lot in the direction of better.
The "HUM destroyer" (All from PS Audio) give the equipment the final touch-
and of coarse all the hard selected power cables.
I didnt tested the 8k with the conditioner yet.
A quick test at my friends equipments(valve preamp-standard LS) bring out the result that when its connected to the amps,that the sound gets cleaner but is limited for the dynamics.
We didnt tested the conditionor at my friends stuff.

The compression of the dynamic of the filter(Duett) get "fixed" by the conditioner.You have to take the filter in series "before" the conditioner, otherwise the sound gets limited.The PS audio "can" correct the change in load of the amp.This experience i have with sources-have to try it wit the DSP.

So only a conditioner doesnt save all-that is the bad news.
One reason to use it beside the current sonic advantages,
is that you get better future proved with a conditioner as without.
But dont try the premier without a filter in front-it makes no sense in my case.

Andy, prepare everything so you can easily change from 1 to 3 phases and listen to it..

Robert