Our great mains

[listening]

That's a very interesting discussion! The sound engineers in the recording studios must be faced with the same problems (depending on mains?). How do they asure the correct environment?

Georg

[listening]

That's a very interesting discussion! The sound engineers in the recording studios must be faced with the same problems (depending on mains?). How do they asure the correct environment?

As I have seen in Articles the mains supply is very good planned. At first they are using the three mains phases for different electronic devices: The first for audio-devices, the second for video and the third for "ordinary" devices. Then the voltage is stabilized by a mechanic or magnetic stabilizer and at least an active filter ist used sometimes supplemented by a passive filter additionally.

Georg

[Nick]

Peters findings have helped here.

I was defiantly suffering from “bad day sound syndrome”. Sound could be very different (relative to what I know could be delivered), to the point that I would try to listen and then just turn off and come back later to see if things had improved. The last couple of weeks things have been stuck in a rut with poor sound most of the time...very frustrating  .

Almost all of the system has been powered until now from one double wall socket, with only one of the active subwoofers being powered from a wall socket across the room. At the wall outlet both sockets were in use with a couple of 4 gang extension leads in series to get reach and sockets to the right locations. The PC, Monitor, DAC, Amplifier, second active sub and a linear power were all plugged in sort of randomly depending on what was being done at the time. This is not quite what Peter is describing I think, if I understand correctly in Peters house there may be use of PE in separate ring mains / wall sockets / supply phases ? Anyway there were some relative earth voltages between components in the range 0 to 15mv.

Out came the old 4 socket extensions and everything was plugged into a single 8 socket extension using only one of the wall socket points. The active sub on the other side of the room still uses a separate socket but this does not seem to drive additional PE voltages. The result is that the relative earth potentials have dropped to between 0 and 0.5mv, and the sound seems back to normal    I have not done many system power cycles so it may be that bad day sound comes back but there was certainly an easily detectable change when the 8 socket extension was connected.

Thanks Peter for posting your thoughts and findings it has made quite a difference, I hope it proves to be a long term solution to bad day sound.

Nick.

[Scroobius]

Hi Peter

Very interesting. My PC is on the main house ring (with the fridge the TV etc) and all the audio devices are on a separate dedicated spur back to the main distribution board. The idea as you suggest was that the "PC could spit its earth rubbish" onto the house ring. So I got my DVM out and with the PC running and the audio devices also running I measured the voltage between the house ring PE and the dedicated HIFI spur PE. In my case the voltage measured was 0 volts. I have short PE runs back to the dis box and recently much of the wiring was changed in the main house ring main so maybe mine is not a typical example.

But I think that you have a very good point clearly (now you have pointed it out) connecting devices to different mains groups (rings) does not appear to comply with the requirement of star earth requirements where everything must connect to a single point. In fact a normal house ring main where the PE connects to everything and then two connections at the distribution board does not seem to be a good idea in respect of star earth requirements. So a dedicated hifi spur (one PE connection ie no ring) looks an even better idea now after your post. I have moved my PC over to the HIFI spur now anyway just to be on the "safe side".

All the best

Paul C

[GerardA]

When everybody takes there DVM's out, then another small trick is to test the best way to put your plugs in.
Remove all connections from other equipment, measure voltage between safety-earth and mass of one pice of equipemt, turn the wallplug around and measure again. (AC and DC)
The lowest measured value is the best, do this for all pieces of your equipent and put a small piece of red tape on the correct side of the connectors and the wallplugs.

PS, But why Peter is your voltage so low? That does not sound like an earthing problem...

[manisandher]

Peter's findings are exactly the reason I went for a 'star earthing' system  (see http://www.phasure.com/index.php?topic=1445.0) - all components (including the PC) have 0V between them. HOWEVER, there are a couple of things that I feel need to be done over and above this for the best SQ:

1. The earthing system should have an ultra-low impedance to ground. This may save your life some day. But apart from this, any noise generated by components (think switching power supplies, etc) will have an easy way to ground, and therefore be less 'tempted' to travel across interconnects to get dissipated.

2. The earth used for the music system should be isolated from that used by the rest of the house. Now, this poses a real problem, as the Neutral is bonded to the earth at the inlet to the building (in the UK at least). The only solution I know of is to use an isolation transformer.

Mani.

[BertD]

The lowest measured value is the best, do this for all pieces of your equipent and put a small piece of red tape on the correct side of the connectors and the wallplugs.

Thanks for the reminder (this IS important!) but how is this done when the signal ground is connected to the mains ground (earth)? Use a socked without earth? How about safety then?

I am asking this because there is a lot of equipment on the market where the signal ground is connected to earth (usually the housing of the equipment which is then connected to the mains earth). Manufacturers do this to bring their own noise down, the most easy way to reduce hum...

The trick above works on equipment that is double isolated (i.e. power cords without earth connection) but how about the other equipment like the NOS1? The NOS1 is connected through earth through the mains cable but also through the DVI-cable passing the PC and then connected to earth again...but also the signal ground is connected to earth?

Peter, why is that? To my idea the signal ground should never be directly connected to the mains ground (earth) in the first place? Mains earth is for safety only...and it is a free ticket for noise present on earth to infiltrate the signal ground, isn't that the problem you have besides the Voltage changes (combined with DC perhaps too)?

Bert

[PeterSt]

Bert,

Actually you pin pointed the most important "phenomenon" of it all : how to get independent from the other equipment, at the same time not producing noise yourself. At least that is what I always had in mind with the ground the design of the NOS1. Also, I had some great examples, and you may recall ... your own amplifiers. Remember ? (mind you please, this is not at all about someone's ground design, and especially not yours for this "example" ... and instead it is about the necessary required independance from the other equipment). So. I'm referring to your "within the blink of an eye" cutting the signal to PE wire in ONE of the amps, just to avoid some perceived ground loop, at testing a signal with just one of the amps, the other one being open and out of reach for testing.
And so indeed your both amps (4 actually) are still the example for at least me and the NOS1 to cover for all, just because they create the problems. ... Which is good, because anyone can create equipment like that.
And for you fun and background : in my momentary setup (actually all being well again at the NOS1 side) I only yesterday evening had to move your amps from PE connected to not PE connected, because now I have a sizzle through the speakers otherwise ...
(btw, awaitening the final solution for this new "mains setup")

So ...
So the problem is exactly about the necessity for a signal ground reference which theoretically can come from a connected chain where all is creating a floating ground which is equal in each device ... but which is rarely the case. Btw, the NOS1 does this, but if e.g. my active crossover does not (you know what I'm referring to) current will be flowing from the one equipment case to the other, and the transport means will be the shield of the interconnect ...
Not good.

Having said this, the NOS1 is virtually (!) floating, unless I missed something somewhere (see below for further explanation).
Unless I overlooked something or made an error in the mean time (during real production). And indeed I have the example of that :
Those without the little volt meters inside (like yours), have an error in the connection of the display, which is not isolated from the case, that creating a strange (and unwanted) direct connection via the PC over USB when the display is connected. However, since the display is not in use yet, I let it be so far since the solution is super simple (connect the display (3 points) with nylon washers).

But there is more, and it is not all *that* easy ...

The version without the volt meters have general ground connected to the case. This is not explicitly signal ground, but the ground planes from the PCBs (not PSUs). And, since signal ground obviously come from the PCBs (ground planes) at some stage, signal ground *is* connected to the case, while the case is connected to PE. And so ... so you are right afterall, but not litterally spoken and certainly not if it were about how ground paths should go where, and whether signal could pickup current flowing through the case. And not to forget, I measure, and all measures is just fine.

The NOS1's with litte voltmeters are 100% floating which -I think- works out for the better if only people have their further devices in the chain in order, which could be something to anticipate upon, and in the end is available as an official upgrade, although I never talked about it publically and I rather (let) apply that upgrade for people with noise etc. problems (but reports about that are zero so far).

Again :

Manufacturers do this to bring their own noise down, the most easy way to reduce hum...

I think this is may be true, but at least for me it didn't work like that, and here too it is coincidentally you who indirectly pointed out how useless this is. Well, in theory. This is about my ever back email that I did my stinking best to let all inherently work with good measurement results, but as soon as all was connected to the main amps, the noise was all over because the main amps had signal ground connected to PE, BUT the main amps were not PE connected, so it lacked the proper reference (and ground potential difference). So, if you think back about this, now you know why I indirectly referenced to PE myself in the first batch of DACs - because otherwise people with amps like mine would have a problem.
(the story is a bit longer, but I'm sure you get the grasp of it)

The NOS1 is connected through earth through the mains cable but also through the DVI-cable passing the PC and then connected to earth again

IMO this is the most normal within itself;
Not thinking about the signal ground connected to PE in this case (which actually is unrelated in this context, and which for the later NOS1's indeed is the situation), this connects the shield of the DVI cabe from actually the PC case to the DAC case. If this hadn't been done like this, the ground wire within the DVI cable would have been used instead for this, so the noise from the PC would be carried over the "DVI signal".
There's one little annoyance with this (well, for me), and that is that in-DAC this shield signal is connected to the PCI ground plane and from there it's the indirect-to-signal-ground situation again (which I rather had avoided, but which is impossible). Anyway, here too the later NOS1's have complete isolation from the DAC case, so that too is not connected to PE now, so really nothing is connected to the case, except PE itself.
Btw, since this is my momentary situation, this setup perfectly allows for not have the case PE connected (but the PC is), which exactly was my "solution" to my sudden noise problems (but amps (everything) has to be disconnected from PE now), and at this completely floating situation at least works (by now worked) for me as the solution. But mind you, this already stops working when the NOS1 output is made floating by itself, like it would be the situation with output transformers (which again isolate). So, here it would take a direct connection from the primary common to the secundary common (which is "created" ground), or otherwise I could not find a solution without PE (and my amps).
See ? it is not all *that* simple ...


The whole situation seems a lot more complicated to me than we usually think about it, which mainly is because of the dependancy from other devices out of our control. But also because of the reactance of interconnects with other devices up to the sheer possibilty of measuring 5V USB between (PE connected) case ground and signal ground, with 0% connection of any ground anywhere (no DVI cable, no interconnects), USB ground cut. In this situation the ground flows right through the air, although it will be inductance impeeded (think transformers), so things even happen which we can't physically see. This by itself is about a case easily being able to act like an antenna, only because PE is floating so to speak, while in the mean time (magnetic) inductance is put on the case by means of the content. Ehm, better connect that content then ... which means connect signal ground to PE (directly or indirectly).

Earlier I found some paper which explains all rather well for the insider, but just this morning I found a derival of it (from the same universaty in Sweden) which I guess everybody should read. Just try from top to bottom as it is only 10 pages, and without real understanding you will at least get the notice of what just *is* going on, and that there's actually no good general solution (meaning : one manufacturer creating a device which will work for all without any problems). By pure coincidence it uses a PWM regulated pump as noise source - which is exactly my own situation, which in the far end is great because that too must be covered for, might you have such an enormous noisy device in your environment; If all is connected well, nothing is seen from it (with general noise of -135dB). If things are not organized so well, it can easily show up up to -60dB (-40dB in rare cases), and this -60dB in my situation was exactly that antenne act of my DAC case, really connected to PE only, neutral and phase cut (I too use the 100% floating setup).

Have fun with this article,

Peter

[PeterSt]

In a separate post, because I think it is the most important of it all, and we can't see it :

The left of the below picture shows a radiating "device". It can be our audio case (with content). How it can radiate is more or less described in the link I provided at the end of my previous post.
In order to understand how devistating this can be for noise or other unwanted signal transfer, look at the right side of the picture. Well, that is just how a transformer operates. So, the right picture actually comprises of a left half and a right half, the left half being equal to the left picture, and when the right half is missing it radiates in our room to whatever can accept it and transform it to energy again (just like a transformer does it internally). In other words :

If you happen to have created that radiating device with no "receiver" opposed to it, it will radiate further into the room. Your amps may start to be the receiver of it. Also, if there *is* a receiver nearby, the energy gets absorbed by that receiver, and there will be no problem further down in the room.

In my view the above can workout two folded :
The radiated signal can be picked up within the device in the case itself and will create noise problems there
or
The radiated signal is not picked up because no proper receiver is there, and now may be picked up further in the room - there creating noise problems.

Of course both described problems will workout very differently.

It may not be so easy to see how the left part of the picture can emerge within itself, but for simplicity let's say that each current flowing somewhere can, and it needs a bit of an "appropriate shape" of the wire which carries the current in order to let it radiate in the coincidental wrong direction (also depending on how "dipole" the antenna shape is, which is related to the directivity and thus spread and short distance, vs. directive and long distance).

On this matter, a small hint to how important balanced interlinks are :
The shield of non-balanced interlinks (SE/RCA) *will* pickup this radiated noise which comes from anywhere in your room. If this were some white noise as such only, it wouldn't be that much of a problem. However, the DC "base" of the signal changes as well, and starts to wobble. In my case this is from plus to minus offset over 100uV, the noise itself being some 30uV (peak-peak). The noise itself (rather white) IMO can not be audible, but the constantly (and random as it seems to me) DC offset ... I wonder.
No such thing happens with a balanced connection, which not only cancels out white noise to some degree, but which will also cancel out the ever changing DC offset to almost nothing.

Peter


PS: And I again promise you ... this topic is still the coincidental begining of a much larger subject, but I can't get my finger behind that yet, since nothing really is on the internet about it. But I guess at some stage I will understand it and report ...

[PeterSt]

Ok, for those who really want to know a little more, and some 4 hours of spare time to read it all through :

http://epubl.ltu.se/1402-1757/2006/64/LTU-LIC-0664-SE.pdf

I (roughly) noted a couple of pages for those who don't want to read it all, but want to grasp the merits of it more or less anyway :

Page 34 , 57, 58, 92, 107 (add 4 pages to each if you want to use the search for page numbers in Adbobe Reader. So, the pages I mentioned (34 etc.) are the numbers printed on the pages themselves).
Although you won't see it much on the pages mentioned, do notice that this paper is audio based.
Do not miss the merit of the "Modulated Switch Frequency" little subject on page 107, which (when you read the whole paper) tells you that devices which radiate heavily at certain frequencies, get tested OK because they apply spreading of that one frequency, the original peak now being low enough (and which peak can be at 200KHz, see PS below), now returning noise throughout the spectrum.




PS: Keep in mind that no regulations/norms/standards etc. exist for radiation under 150KHz. This is believed to be harmless. Sadly this allows devices like my PWM regulated pump (which is only an example) to radiate at 17.8Khz. But also my fridge does (at 15.5KHz or so), and who doesn't have that. But even more important is that this is square waved distortion, which means that only the peaks show up at mentioned freuencies; in the end the whole (audio) spectrum is influenced, since square waves comprise of an infinite number of sines of all frequencies ...

[Scroobius]

Well this is very interesting reading following what happened to me last night.

In my post above I said that my PC was connected to my house ring main and my audio components (mains amps & NOS1) were connected to a dedicated "HIFI Spur". I also said that I could not measure any voltage between the house ring main earth and the dedicated HIFI spur earth (so I thought it was *OK*). But regardless of that last night I connected the PC to the dedicated hi-fi spur along with the main SET amps and NOS1. So then I sat back to listen to music and sat there open mouthed. There was a very big improvement in sound quality I mean very very big everything imaging dynamics detail fluidity (something I did not think possible). To begin with I thought it was just a "good sound" evening or that I was kidding myself but no this was a too big an improvement. So just to check my sanity I asked my old HiFi mate (fellow geek!) David who is well familiar with the sound of my system to check it out and likewise he confirmed the improvement.

So what has happened? to begin with I thought that maybe it was something to do with the sound card and PCIe card being on different earths. But that does not appear to be the answer if my NOS1 is completely floating as Peter states above. So perhaps it can only be that the RFI being generated by the PC is being disposed of much better now. The HiFi spur earth is very good and has a short (10m) run back to the distribution box earth point. But this would not seem to explain such an improved SQ. Any ideas anyone?  by the way my main SET amps have the std tube arrangement of a PE to the cases and a signal earth separated from the PE by a 100 ohm resistor.

Boy does this system sound good now!! the dynamics are enough to wake the cat next door!!

PC

[PeterSt]

Hi Paul,

Well, interesting !
But to be honest, while you seem to be the only one really reporting about two PE rings, you also report no voltage difference between the two, and this puzzles me a bit. If not about your not perceiving a V difference, then about my situation just having that. So what is wrong ?

Let's say your system. Haha.


Ok, I had an enormously long reply at first, but for now I'll stick to the notion that when the signal ground from all your devices is connected to PE (or at least the two which will virtually interconnect the PE rings), the PE rings will be interconnected as well and no voltage will be seen over them.
What this means for your further situation and whether now using two PE rings or one makes a difference - was my reply about, but it's too much guessing from my side. So I stick to this nice short text for now ... (but have saved the long one)

Peter

[Scroobius]

Hi Peter

I think you are probably right.  One thing all this highlights is just how important earthing is. Well I kind of knew it was important before but now I * REALLY * know how important.

Great that you brought this important subject up Peter.

All the best

PC

[Scroobius]

Hi Peter,

Perhaps you could clarify this point. As I understand it ONLY the case of NOS1  is connected to PE and everything inside NOS1 is NOT connected to the case. So as far as I can understand from what you have said the sound card inside NOS1 is connected to the PC earth via the DVI cable and the line output amp card earth is connected to the SET power amps signal earth via the RCA interconnects. Also presumably inside NOS1 all the electronic module earth planes are connected together.

So in my system as it was before with the PC connected to the house ring main and the other audio components (SET amps and NOS1) connected to separate dedicated hifi spur I would expect that the earths would be connected but there would be a 100 ohm resistor (the SET amps have signal earth and PE separated by 100ohm resistor) between them (maybe 50 ohm as they are in parallel). Not a good earth arrangement I agree but maybe I will check again to see if there is some small voltage between the earths (or maybe I will just listen to music  )

All the best

PC

[Nick]

Paul,

A decidedly low tech contribution to a complex subject  .

A few years ago when I lived in a different house that had PE bonding to the copper water system, I noticed that bonding points were a little corroded so I went round and cleaned and tightened up all of the live and neutral ring main connections and cleaned and tightened the earth bonding points. At the end of the exercise the was a definite audible sound improvement. I guess your dedicated audio ring main would be relatively new and would not be a candidate for this, but its interesting that such a simple measure helped so much.

Come to think of it, I'v not done this in my current house, maybe a job for the week end ....

Nick.