Home noisy cabling setup: can I improve it without changing the cables?

[antcollinet]

Not at the moment and during this testing, just interface to Mackie - Mackie to Rotel and Rotel to HP ampli.

A moment ago I tried to lift the ground in the USB cable from NUC to interface placing a bit of isolating tape on the first stripe to the left in the USB A plug, but nothing changed.

You may find the noise comes back when you reconnect the HP amp to to PC and Rotel.

I've taken you sketch, added the mains earth connection for your PC and the Interface, and drawn at least one earth loop in orange.

 

[fabiospark]

Tomorrow I will steal from my daughter a box with a power socket and a "ground/lift" switch I made for her problems between her Yamaha THR10 guitar amp and her laptop a while ago and then I will put it on the power of all the devices, one at a time. That would easily let me break the orange loop in different places to see what happens and I'll report back.
Thank you and thank everybody for the time you are spending trying to help me solve this problem. For me it's easier to find the time 'cause I'm COVID positive and locked in the house...
fabio

 

[antcollinet]

... 'cause I'm COVID positive and locked in the house...
fabio

Ouch - get well soon.

 

[Holmz]

I read this after I posted my last post (#50) and I can confirm that even a 1m RCA meters away from the NUC picks up the RF noise, even if maybe at a lower level.

Even bats with their exceptional hearing, did not evolve to pick up RF.
You more likely have a ground loop problem.

If it is “RF”, then it would be lower frequency magnetically induced currents… in the audio band.

…
For me it's easier to find the time 'cause I'm COVID positive and locked in the house...
fabio

Get well.
We have found a link to bats.

 

[fabiospark]

Thank you for the wishes. I've got three days of temperature to 38,5°C, nose sometimes running and other times locked, cough and a nasty sore throat but I'm getting back to normal every day.

This morning I feel REALLY better because... lifting the ground on the AC side of the NUC power supply did the trick!
I'm not getting any noise at all even from the RGB (RCA round) cable and even if I cranck up the Head Box HP1 volume. Not needing the balanced lines any more I removed the Mackie from the chain and now have only:
stereo unbalanced (RGB) from interface to Rotel stage input + stereo unbalanced (RGB) from Rotel zone 4 out to Head Box input 1 + headphones on Head Box HP1 output.
I also tried back the RCA flat from Rotel out to Head Box in and the difference between that and the RGB one is minimal considering that the flat one gives a tiny little noise only with the HP voulme crancked all up (I usually use it between 9h and 12h).
So I consider this side of the "noise" problem, solved and I heartily thank everybody for the help and the patience.
To the mods, if you think it could be useful, consider adding the word "solved" to the title.

After that, making some other test I noticed that connecting the audio out of the DESK PC to the input 2 of the Head Box, with a stereo flat RCA <1m, I can hear a little noise with the Head box switch on ch 2, but the same noise is a little louder when I switch the Head box to the channel where there is the cable from Rotel.
To me that noise sounds a little like the one of a very distant ultra light plane...
It's not comparable with any of the sounds you can generate here: https://mynoise.net/NoiseMachines/50HzHumNoiseGenerator.php

Changing visualization from an almost totally white page to an almost totally black one on the main screen of DESK PC, the noise changes frequency and it seems that with the dark one it also gets a little louder.
The monitor is an old Formac one with, I think, a fluorescent lamp as a backlight source.

Thanks.
fabio

 

[antcollinet]

Thank you for the wishes. I've got three days of temperature to 38,5°C, nose sometimes running and other times locked, cough and a nasty sore throat but I'm getting back to normal every day.

This morning I feel REALLY better because... lifting the ground on the AC side of the NUC power supply did the trick!
I'm not getting any noise at all even from the RGB (RCA round) cable and even if I cranck up the Head Box HP1 volume. Not needing the balanced lines any more I removed the Mackie from the chain and now have only:
stereo unbalanced (RGB) from interface to Rotel stage input + stereo unbalanced (RGB) from Rotel zone 4 out to Head Box input 1 + headphones on Head Box HP1 output.
I also tried back the RCA flat from Rotel out to Head Box in and the difference between that and the RGB one is minimal considering that the flat one gives a tiny little noise only with the HP voulme crancked all up (I usually use it between 9h and 12h).
So I consider this side of the "noise" problem, solved and I heartily thank everybody for the help and the patience.
To the mods, if you think it could be useful, consider adding the word "solved" to the title.

After that, making some other test I noticed that connecting the audio out of the DESK PC to the input 2 of the Head Box, with a stereo flat RCA <1m, I can hear a little noise with the Head box switch on ch 2, but the same noise is a little louder when I switch the Head box to the channel where there is the cable from Rotel.
To me that noise sounds a little like the one of a very distant ultra light plane...
It's not comparable with any of the sounds you can generate here: https://mynoise.net/NoiseMachines/50HzHumNoiseGenerator.php

Changing visualization from an almost totally white page to an almost totally black one on the main screen of DESK PC, the noise changes frequency and it seems that with the dark one it also gets a little louder.
The monitor is an old Formac one with, I think, a fluorescent lamp as a backlight source.

Thanks.
fabio

Just bear in mind - with the ground lifted you now are operating the product without the correct safety grounding. You should not consider leaving it like this as your normal operating mode.

 

[fabiospark]

Just bear in mind - with the ground lifted you now are operating the product without the correct safety grounding. You should not consider leaving it like this as your normal operating mode.

Yes I know and I will think to make something different to be able to lift the ground only when it is needed.

But this is also what the Rotel does by design as it ha a two prong power connector an cord. Having a metal body I wonder if it is compliant with Italian or European grounding rules. According to them you must avoid grounding a device only if it is doubly isolated and that reports a concentric double squares symbol on the plate. We call it "second class insulation" and it means that you have to have two layers of insulating materia between the live parts and the outer structure of the object.
I don's see anything like that on the Rotel...

Thanks.
f.

 

[antcollinet]

Yes I know and I will think to make something different to be able to lift the ground only when it is needed.

But this is also what the Rotel does by design as it ha a two prong power connector an cord. Having a metal body I wonder if it is compliant with Italian or European grounding rules. According to them you must avoid grounding a device only if it is doubly isolated and that reports a concentric double squares symbol on the plate. We call it "second class insulation" and it means that you have to have two layers of insulating materia between the live parts and the outer structure of the object.
I don's see anything like that on the Rotel...

Thanks.
f.

If it doesn't have a ground it must be double insulated. But bear in mind double insulation can just be 8mm spacing.

And rather than messing about lifting the ground - just get yourself an isolated signal between Nuc and Interface.

 

[fabiospark]

If it doesn't have a ground it must be double insulated. But bear in mind double insulation can just be 8mm spacing.

And rather than messing about lifting the ground - just get yourself an isolated signal between Nuc and Interface.

OK, but what about the other unchangeable RCA unbalanced I will still have to use: Rotel to Head amp, PC DESK to Head amp, PC DESK to Rotel, Rotel pre to Rotel ampli... and so on?

 

[Holmz]

OK, but what about the other unchangeable RCA unbalanced I will still have to use: Rotel to Head amp, PC DESK to Head amp, PC DESK to Rotel, Rotel pre to Rotel ampli... and so on?

You have to be joking right?
What other problem is there?

You lifted the ground, breaking the loop that’s makes a gourd loop.
The noise went away.

You’re not still on that thing about RF sneaking in from the aether are you?
Just listen to @tonycollinet

 

[antcollinet]

OK, but what about the other unchangeable RCA unbalanced I will still have to use: Rotel to Head amp, PC DESK to Head amp, PC DESK to Rotel, Rotel pre to Rotel ampli... and so on?

As far as I understand - you've said lifting the NUC ground solves your problem. So isolating the NUC ground from the rest of your system via an optical link should have the same effect.

 

[fabiospark]

You have to be joking right?
What other problem is there?

You lifted the ground, breaking the loop that’s makes a gourd loop.
The noise went away.

You’re not still on that thing about RF sneaking in from the aether are you?
Just listen to @tonycollinet

I was listening to @tonycollinet who said this:
"And rather than messing about lifting the ground - just get yourself an isolated signal between Nuc and Interface."

and I misread the last sentence that in my mind became: "get yourself an isolated signal between Rotel and Interface".

So I thought he was telling me to put the NUC power supply ground back for safety reasons (and so the noise would have come back) and to use balanced cables from interface to Rotel ("isolated signal"), hence my question about the other unbalanced RCAs. My fault I read the post superficially and replied according to my misinterpretation.
I read that sentence right as it is, only after your little rap on the knuckles...
Thank you.

If anybody has direct experience with USB isolators that doesn't cost a fortune I'll be glad to start to think what to do to get that "isolated signal" between NUC and Interface.
Thank you again.
f.

 

[Holmz]

As far as I understand - you've said lifting the NUC ground solves your problem. So isolating the NUC ground from the rest of your system via an optical link should have the same effect.

Yes and no @tonycollinet

…
This wiring has always been a little noisy but since I got the NUC, when I switch it on, a strong RF noise is added so I'm considering to
replace it with a balanced (differential) wiring, then putting a stereo balanced-to-unbalanced converter near the ampli.
…

So it might be another ground loop was also there before.

…
If anybody has direct experience with USB isolators that doesn't cost a fortune I'll be glad to start to think what to do to get that "isolated signal" between NUC and Interface.
Thank you again.
f.

Those are worth a try.
I though I ordered one… but I do not see one around.

 

[fabiospark]

Please read my post after yours to understand my previous last post...

As far as I understand - you've said lifting the NUC ground solves your problem. So isolating the NUC ground from the rest of your system via an optical link should have the same effect.

So are you talking of a galvanic USB to USB isolator?
Do you know of any high speed one? My interface has 8 channels and I'm afraid a full speed couldn't be enough.

I looked around for these isolators yesterday but in the end I felt that the only one trustable is the Intona but it would cost as half the NUC or the interface...

Thank you.

 

[antcollinet]

Yes and no @tonycollinet



So it might be another ground loop was also there before.




Those are worth a try.
I though I ordered one… but I do not see one around.

Please read my post after yours to understand my previous last post...

So are you talking of a galvanic USB to USB isolator?
Do you know of any high speed one? My interface has 8 channels and I'm afraid a full speed couldn't be enough.

I looked around for these isolators yesterday but in the end I felt that the only one trustable is the Intona but it would cost as half the NUC or the interface...

Thank you.

I was actually thinking of USB to optical - along the lines of the cheap behringer device I linked earlier.

But that is not going to fix your 8 channel problem. No, I don't know of any inexpensive high speed USB isolators. Sorry.

Do you need to input audio from the interface to the NUC also - or just output?

 

[fabiospark]

I was actually thinking of USB to optical - along the lines of the cheap behringer device I linked earlier.

But that is not going to fix your 8 channel problem. No, I don't know of any inexpensive high speed USB isolators. Sorry.

Do you need to input audio from the interface to the NUC also - or just output?

No, between interface and NUC just USB to digitally process in a DAW on the NUC the analog audio recorded through the mics connected to the interface.
Editing and mixing is done in the NUC remotely controlled from the desk PC with remote desktop, with the audio coming out of the interface.

 

[mcdn]

Why wouldn't you just use digital out of the Focusrite to digital in of the Rotel? Use the optical interfaces and you completely remove any electrical grounding/loop issues.

 

[mcdn]

Why wouldn't you just use digital out of the Focusrite to digital in of the Rotel? Use the optical interfaces and you completely remove any electrical grounding/loop issues.

And actually, same question for the desk PC and media box. That Rotel seems to have loads of optical digital inputs, using them would get rid of all your noise issues.

 

[somebodyelse]

If you don't mind evaluation modules TI's ISOUSB211DPEVM would probably do the trick. Neither that chipset nor the ADUM4165/6 seem to have made it to the mass market yet.