XXHighEnd

After having a noise problem (and still have, but...), I was wondering how to connect things on 2 separate circuits, but also which component needs to be on a Protective Earth (PE = ground) and what should not (Non PE).

I also wonder if Non PE and PE can be on the same circuit or not.

I know that normally the digital ring should be separated from the analog ring. But, apart from wall warts and PC power supply, what should be considered "digital", as opposed to analog ?

Knowing that I have:
A)  a 2 prong "wall wart" power supply (AC > DC, 120v > 5v) > iFi iUSB > external SSD 120GB (OS + XXHE) > Esata > PC

B)  a 3 prong cable for a linear power supply (AC > DC, 120v > 12v) > external spinning HDD 2TB (music) > Esata > PC

C) PC > USB > NOS1 dac > analog unbalanced interconnects > preamp > analog unbalanced interconnects > power amp. Each of these components have 3 prong connection.

D) 2 subs are connected to a pair of outputs from the preamp (unbalanced interconnects) (the preamp has 2 pairs of outputs, so 2 x left AND 2 x right channels) (2 prong connection, class D amp for each sub).

I have 2 different circuits. They are on the same house electrical panel. 120v AC means that there is a "hot" wire, a neutral wire (that goes to the same rail as the ground back at the electrical panel) AND of course (when it's a 3 prong connection), the ground.

How should I connect all of these, provided that I have 2 circuits (each having a powerbar), then once this is done, what to connect to PE (Protective Earth) and what to connect on a NON PE ?

Sorry if I describe too much, but at least once this is settled, I will be able to better identify what noises are still there...

Sorry also for the bad English (as usual)...

Thanks :)

Alain

Hi Alain,

Without looking into the details of your post, this is the general setup :

- Sell the preamp;
- Disconnect the subs;
- Do not connect the NOS1 to PE. Same for the power amps.
- Connect the PC to PE.

I know, this first (preamp) may not be easy to try (scared) so save that for the last option.

But I am just thinking ...
I never tried this, but what about measuring AC voltage at the amp outpts ? So, disconnect the speakers and just measure AC. Maybe it does not work with a multi meter because of the too high frequency, but maybe it does to some extend.
And, take care that the amps don't switch off because of seeing no load. When that happens, find yourself a maybe 10Watt 8 Ohm or so resistor and shortcut the outputs with that (just connect between plus and ground (minus). So :

- Connect multimeter to the outputs (AC);
- Switch on. Don't play anything;
- Measure including preamp;
- Measure without preamp.

Don't ask me what is allowed to see, but theoretically only maybe 30mV at most. If it can be measured at all.
I thus never tried, but here the analyser would show 8uV (NOS1 noise) with a (power amp) gain of 20. This makes it 100uV or so.
My mentioned 30mV is way more, but I think inaudible.

The key of this attempt would be to see a difference between preamp+amp and amp only. Well, sort of, because when the preamp shows significant noise to some extend, it could be the cause of your problems. Not talking about deteriorated sound, but about implying a groundloop somewhere.

Good luck and let me know !
Peter

Well I haven't sold the preamp yet, but I finally found the right combination to have it all working !

Paul's help had me understand part of what a ground loop is made of. Reading a little more helped me to get a little deeper into it.

As I understand it, in gross the principle is as follow: 2 components that are not interconnected in any way should be connected to Earth when there is a mean for it (a 3 prong connection).

As soon as you connect 2 components together (interconnect that ties them together), a "triangle" can appear. It is not always bad, but it can trigger a ground loop. When this occurs, to correct this, all that is need is to remove the connection to Earth for one of the 2 components, since ground will travel between the 2 components and exit through the component still connected to Earth.

It is not automatically how it turns. Having 2 components connected together, with each of them on a different AC circuit still follows the same rules, as it normally lands on the same rail in the main electrical panel. Well that would be like this here in Canada.

But don't ask me more ! There are lots of other situations (hadware grounding inside a component), between themselves, etc... I already have forgot the path a few billion electrons have chosen to follow since I did all these attempts...

So, logically, as I understood it, if I have a PC, DAC, preamp, power amp, all connected together, BECAUSE I HAD A NOISE, this meant that I should only have one of these 5 components connected to Earth. Easy...

Not so !

That was my starting idea. Like I said, this is a gross view of a situation where there could be a ground loop.

So with this in mind, I only connected the PC to Earth and lifted all the rest.

But I forget to descrie the noise I wanted to get rid of. It was not a "hum" as we generally think of when someone says "ground loop alert !". No, it was a thin sound, some kind of frequency that maybe someone has heard when an electronic chip starts "singing" depending on the amount of current going through it. Or you could compare this to a light bulb emitting a sound when you play with a dimmer...

So, I was not sure if I was going for a ground loop or for a defective piece of hardware... Lucky me... :(

It took me a long time to discover how to get rid of it. Today, finally, with the help of an old integrated amplifier I have here since 1984 (NAD 3020B), I finally stopped hearing that noise. This old but faithful little amp as a 2 prong connection ?

So now I have this configuration:
- PC - to Earth
- USB cable (nothing special about it)
- NOS1 dac - Not connected to Earth (2013/09/17)
- RCA interconnects
- Preamp - Not connected to Earth (2013/09/17)
- RCA interconnects
- Power amp - Not connected to Earth

All of this is on the same AC outlet by the way ! I will eventually separate them, but at this time the need to simplify things had me doing things like this.

I know that Peter suggested to me to have the Earth lifted for the NOS1. I tried it but to no avail. What worked for someone will not necessarily work for someone else.

What are the conclusions today ? I don't know. I would not be honest to say that I understand all of it. It was a matter of "trial and error"...

For those who will eventually encounter this situation: if you have old speakers you don't mind to damage, please use them instead ! I almost blew my speakers while doing something that I thought was not dangerous.

It can help to have a few spare components. I have 3 amps here, so I was able to eliminate some components I was questionning out of the equation.

Playing with protective earth is not a subject to take lightly. It can be dangerous - for you and your equipment.

Alain

Ha Alain, another victory in the Noise Department ! Super.

Let me add a bit of a cautious conclusion :

First, to make this clear better to others, what Alain did was replacing is Spectral amplifier with the NAD one. That finally removed the noise (hey, Alain has been frustrated about this for well over a month I'd say). The NAD just doesn't have an Earth connection, so it was Alain's idea that "the amplifier" should not be connected to Earth (PE). The idea was good, because when the Spectral was moved back into place but now with PE lifted, all was finally right.
(I hope I have this correct).

Now my cautious conclusion :
It was my advice to create a mains extension block without PE and with a sufficient amount of outlets to connect all the devices. Now try all the combinations possible, starting with all devices in that non-PE block and to one by one connect a device to PE. Then two of them. And so forth. The more devices needed in the chain, the more combinations to try of course. So :
Alain, I don't think you did this and it took a couple of weeks of frustration more ...

Assumed I am correct with the above (and I think I am), it is important for me helping with such issues that people actually do what I ask them to. Of course, nobody needs to do that, but the point is that when 3 days later the message is "still can't remove that noise", I can only think that this "mains block" thing has been attempted. And next we're all on a dead end.

This is nothing to blame anyone for, and it is also not about wasting time or anything, but it *is* about not being able to get there while it obviously (in this case anyway) still can.

Of course, I am to blame that people now thing that when audible noise is there it should be taken out, no next get obsessed about it. This obsession IMO is justified BUT you need to know the "noise specs" of your power amplifier. And then still I'd say that no amplifier (also not tubes) will produce so much noise that it will be audible on whatever high efficiency speaker. And otherwise that specs should say -90dB to be on a very safe side, but in my opinion it realy should be -70dB. Well, no amp carries such poor specs (I think).

I have to emphasize it once again : I have lived almost all of my life with noise through the speakers, which for the largest part didn't seem a problem because of using a preamp which rendered that noise inaudible anyway because of sufficient attenuaton (which in the end doesn't help a thing because the SNR doesn't change a bit of it). Next I lived with "acceptable" noise through my high efficiency speakers for I think a reay or two. "It won't go otherwise" I thought. Until I found the (SQ) importance of it, and sat down for it like Alain (and more) did. So I learned it can be done.
Today ? Today it regularly happens that there's noise again (new amps etc.), but I *know* I should be able to get rid of it. And so it always happens.
Keep in mind : this assumes "no preamp" or other means of analog attenuation. So, *that will* imply noise and looking at specs of the preamp or attenuator is useless (let's say they always lie). This in other words : you can use a preamp/attenuator if you think this is better, but always check the noise without that. All OK ? then move back in the preamp/attenuator. Then you will know (if the preamp/attenuator injects the noise on its own, hence outside of groundloops, which latter *still* can be in order of course, but you will know the cause now and can proceed from there).

Great that you persisted Alain !
Regards,
Peter

I like this idea.  Does the construction of this mains extension matter much, or could it be any outlet box with the ground wire cut?

Can be anything - if you are like me and think that power cords etc. don't matter much anyway. But remember, this is for trials only, and later you can make a robust "PE-less" block of it.

But don't get yourself stuff with a nice (red) led in it ... (to show the switch is On).

Peter

Because.....??

If you turn off the light my room is lit like the Amsterdam "walletjes"  ;).
Ik kinda like that!

Regards, Coen

Light dimmer effects ?
:)

PS: Just watch that led in there flicker.

Hi Peter,

Well yes, you extracted most of the essence about what I did and should have done. I was kind of "anarchic" (random) in my way of testing, so it took me ages to finally correct this problem. At one time, I even thought the NOS1 was the culprit...

From what I have seen the last 2 years, I can say this: Peter is one (if not the best) of the very few persons I know that can extrapolate situations from afar. We must always remember that doing a diagnostic through distance is not an easy thing. But Peter has so much experience and is so cunning that it's almost as if he was here, in this living room, knowing what is wrong ! And that in itself is a rare quality.

And yes, a powerbar with the earth pin removed should be handy to use, but I would advise against twisting the pin in all directions when you remove the Earth prong. I did that once and... I had a short circuit... The ground wire inside went loose and touched the hot wire... So if you decide to have such a powerbar, maybe it will not be a bad idea to replace the "head" (the 3 prong connection) with one that you can install yourself, after carefully removing that earth prong. Or at least "cut" the prong, don't twist it... 

Anyway, thanks to Peter for his patience. I can be quite insisting with all my emails about different situations.

This forum is not like any other I have been attending. There is a sense of community here, where people from all different countries are welcome. And even if my English can be confusing at times, I am doing my best to contribute, because it is the way I am, but also it is how I feel we are here for. And I certainly don't let my ego be in the way ! When I don't know, I will say "I don't'" and sometimes I can feel "ignorant", but that's ok. I don't expect others to know everything either.

That is the reason why I share this little situation. And don't forget to ask questions when unsure of yourself :)

Regards,

Alain

Ah Alain, thank you for your so kind words. But it really is not necessary. I am only so glad you could solve the situation which for me too seemed "impossible". Really, it is so difficult for myself already !

OK, done !
Peter


PS: Maybe the best thing in this little noise project was my sort of refusing to let you send in the DAC (and the $$ behind that). That keeps you going you know ... :yes:

Well yes too (about $$$), but I did not feel I had given the NOS1 all the chances it deserved. Nothing is perfect in this world, but...

Alain

They do flicker. I thought they were neon. So I should tear those out?!

Regards, Coen

And about the external hard drives...

When I connected the "spinning" hard drive (powered with a 3 prong linear power supply), I could hear the starting cycle through the speakers, even it the preamp was in "mute"... This, when the PSU was connected to Non PE. With PE, silence...

This also is a matter of "trial and error"...

Alain

Even if you disconnect the earth of the bar at the plug you are not rid of the loops. For that each receptacle in the bar has to be disconnected from the earth.

I made a few cables with the earth wire cut and marked them as such. The powerbar still has earth for the screen of the cable (if present). That would be connected at the powerbar side only.

Regards, Coen

I reckon that everything which flickers does not draw current in continuous fashion. And to nicely put that directly to the mains (which it does) ?
So yes, I smash them out (but usually they are just connected with wires which can be pulled off).

Peter

Ah... Of course... Thanks Coen. Will try to find a powerbar that I can open ;)

Regards,

Alain

Btw, in all honesty what I really do with those bars :

I use the larger ones (with 10 outlets) and assumed the cord (inlet) is at the right side, I cut the PE strips at half of the bar, and cut them at each outlet towards the left. Mind the latter, because otherwise the devices can "PE" interconnect again through that strips which btw is again another means to solve problems (but now you get quite many options, so better stay out of that). Anyway, now the left 5 outlets are without PE and the right 5 outlets are with PE (the bar itself just connects to PE).
This is just a robust bar and now I can change things very easily each day if I want (so this is in permanent use).

Need more outlets with/without PE ? then make another such bar, and plug it into one of the rightmost (with PE) outlets of the first one ...
(which is what I indeed use).

Want to change house ring (etc.) ? then put the main cord of the first bar into something else.

The $$ investment for this obviously is "nothing". But the time you gain when you experience problems is sort of infinite.

Peter

I now see that Coen again was ahead of me (I did not read carefully) :


That's what I meant with : when you don't do this, each device will still interconnect through its "PE" means.

If you are going for the openable powerbar anyway, i think Peters idea is better.

Think of a loop as more than one way current can flow from a to b. If one of these path is long (like via the earth connection), you have a giant antenna for em radiation from mains, mainstransformers and radio, etc. Since the two (note: you can have even more than one extra route) form a triangle or circle or iow loop this em radiation gets into the circuit and make currents run in circles through that loop causing hum, noise etc.

Regards, Coen

I find these ideas quite interesting... "To PE" or "Not to PE" is the question :)

I will go this afternoon look for a good, solid powerbar that I can open. There is still a "grunge" (nothing compared to what I had before) and I suspect it would be between the preamp and amp (on the same Non PE powerbar, but "looping" through interconnects and the ground in the powerbar itself).

Lots of new stuff to test, but this time it will be more fun :)

Thanks guys !

Alain

In the continuation of my hunt for noise, I modded a cheap powerbar to separate the ground between the outlets. Quite cheap inside... I will get a better one.

Well what do I know...

First I can now use the NOS1 with no PE...

Second, I can plug the preamp on PE with no difference...

Still the power amp needs to be on no PE. That was quite clear yesterday when I did my test with the 3 different amplifiers I have.

You may ask why I decided to play again with this. Well, I still have a "hum" with some grunge. Nothing to compare with that annoying frequency that I had previously, but still.

It's the 2 subwoofers... 500W class D amp for each. They "leak" in the preamp...

The male IEC receptacle on each of them has only 2 prongs. No PE for them. Yet I tried with a Non PE powerbar, but of course there was no difference. I played with the preamp on PE and Non PE. No difference.

... My quest is not finished...

Alain

Well, after playing with the recommended "DAC to power amp", I finally had afterthoughts and decided to bring back the subs that I had removed. That means I had to put back the preamp in the chain too.

Among other things, removing the subs was decided because I could not get rid of a grunge that I could perfectly hear in the main speakers.

I know now that if I put the power amp back on protective earth, this grunge disappears.

So this is the actual status:
- With power amp AC ground lifted I don't have the original ground loop noise, but the subs make noise.
- With power amp AC grounded (normal), I don't have the grunge from the subs, but then the original ground loop comes back.

This is not obvious... :(

Alain

May it help you Alain :

I never ever was able to eliminate the additional HF hash my subs imply. It is the most hard to explain how or what is at work, but say that any "frequency" I can measure as an anomaly in my system, gets worse when subs are on. So I don't see any anomaly from themselves, but I see the others getting worse.
I do know though that my subs create a potential which is not on par with the other gear. So for example, when I try to eliminate their implied anomalies by means of additional ground wires from sub's input ground to cabinet elsewhere etc., the sparkles come from it, and what I recall is that the potential difference is 56V or so. But the sparkles tell that really a lot of current is flowing.

I must say that I didn't work on this anymore for maybe 3 years and I just accepted the fact. Today I maybe could do better on this, but today my subs are out of the system ...

Regards,
Peter

Sparkles and 56V flowing on the ground... Not a good start... Thanks anyway. I will keep posting as I evolve in this situation.

Strange that they don't carry a ground prong for a IEC receptacle...

Alain

Same with mine ...
(SVS from the US)

Something has changed since last time I wrote (October 19, 2013) with that grunge that was generated in my main speakers each time I was turning the subs ON.

For personal reasons I disconnected all my things last February and did not use my speakers and power amplifier until yesterday.

Just to recapitulate:
- I had a ground loop problem last year and the only way I could get rid of it was by lifting the power amp PE.
- But after doing this, another "grunge" noise appeared in the main speakers and to my dismay it was coming from my 2 subs when they were ON.
- Each of these 2 problems was in opposition with the other... Putting back PE on the power amp was removing the noise coming from the subs, but the other ground loop noise was back...

Yesterday (April 10) I reconnected everything together, leaving the power amp PE lifted and... I don't have either noise anymore !!!! :)

So I wondered what could have changed since the last time
2 things:
- I removed the iFi iUSB powering my external SSD drive because it cannot power a new SSD that I have now. I have put back the wall wart that came with the iUSB power supply.
- I have isolated the Silverstone USB 3 PCIe controller card AND disconnected the NOS1 black wire (http://www.phasure.com/index.php?topic=2838.0)

As for the electrical circuits, they are the exact same as they were before.

So, I am not 100% sure, but if I had a guess to make, I would say that the isolation of the USB connection from the PC chassis and the disconnection of the black wire in the NOS1 could explain this.

I will probably do some tests in the following times, but it sure is a happy conclusion :)

Alain

That is great Alain.

I recall you talked about that iFi's supply before (about trying its wall wart). So apparently you didn't at the time, or I dreamt it ?

Anyway, for all these noise issues I think always any USB connection matters (things just change). So better avoid USB at all ? :swoon:

Regards,
Peter

Peter,

Ah ! I stand corrected... I wrongly stated that I switched back to the iFi iUSB wall wart, but that's not correct.

I switched back to the wall wart that came with the external enclosure, not the iUSB. The iUSB does not work with the external enclosure anymore. I can't explain why it is so, since the SSD drive is told to use 195mW of power when active, while the iUSB can deliver 5 watts (5V x 1A). Maybe the enclosure itself takes more power than one would expect, but the result is that there is not enough current to power the SSD. Maybe the explanation lies elsewhere, but I can't wrap my head around this...

Regards,

Alain