Sound system chain and ground scheme

[AlainGr]

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

[PeterSt]

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

[AlainGr]

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

[PeterSt]

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

[Mamba315]

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.

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?

[PeterSt]

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

[CoenP]

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

Because.....??

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

Regards, Coen

[PeterSt]

Because.....??

Light dimmer effects ?


PS: Just watch that led in there flicker.

[AlainGr]

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

[PeterSt]

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 ...

[AlainGr]

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

[CoenP]

Because.....??

Light dimmer effects ?


PS: Just watch that led in there flicker.

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

Regards, Coen

[AlainGr]

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

[CoenP]

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... 

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

[PeterSt]

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

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