Calm down, we were talking about a Naim and Chord as per the thread… and you randomly brought in other vendors without initially stating that… please be clear… as it looks otherwise as if you are stating untruths/misinformation as it appeared here.
Anyway I am glad you found a way to connect your Onkyo CD player digital output to your Naim… why don’t you start a new thread advising that?
@Blackbird you needed a grounded coax digital lead. Many on the market. I used an Audiotechnica one in the past and the interconnect had an earth dongle at on end to affix to the chassis earth of any supporting unit.
I suspect your issue was a combination of not knowing the requirements of the Onkyo and wrong cable.
A chord qutest connected to my SN2 caused a large hum through my speakers. I connected another source to the amp which resolved the issue.
@Pedropete exactly my experience with Hugo.
I’m sure this issue was well documented many moons ago on both the old Chord Electronics support webpages and in the old Naim forum.
Pedropete, if you look at the SN2 manual it says
4.10 General Connections Notes
The SUPERNAIT 2 negative input and output connections for each channel are common. The mains earth (ground) should always be connected regardless of what other equipment is used in conjunction with the amplifier. The mains earth only grounds the case and the electrostatic screen within the transformer, and is not connected to the signal negative. In order to avoid hum loops, the signal negative of the whole system should be connected to the mains earth (ground) in one place
Therefore you need to ensure one and only one source is earth grounded.
Chord, like many manufacturers don’t earth grounded their sources, therefore with connection to Naim you should ensure you have another earth grounded source connected to the NAC inputs, or manually earth by careful DIY your one and only floating source.
This has been discussed many times on earlier forums…
This is Naim’s design to star or centralise the ground so as to minimise the noise floor.
BTW of course the earth grounded source doesn’t need to be selected or active for this to work… it simply needs to be connected to the mains, and the audio lead output connected to the NAC input.
I can add that my house and all houses built up to 1994 in Sweden have non grounded outlets in all rooms except bathroom and kitchen. Not sure how that is in UK. But as always it’s the customer doing wrong when using Naim even though it’s only with Naim I’ve had buzzing transformers, ground loop issues etc. Strange.
I think Sweden and Japan are alone in the world for non grounded outlets.
Naim stuff must be mains earthed or not used.
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On my SN2 with the original Hugo in some configurations there was a buzz. If I remember rightly I took a weird from the ground screw to the outside of one of the din plugs and it was resolved. No issues with 282 and any of my hugos
Our apartment in France was the same, presumably to save money when it was built in the 70s, there was even an earth cable passing behind some of the unearthed sockets in the living room. This is one area that could usefully be harmonised in Europe and probably has been by now even if the socket format hasn’t. At least appliances that require an earth would be safe to use anywhere within the single market.
Well a grounded outlet is more safe but if that statement would be true homes in Sweden and japan would be empty of electrical equipment which is not the case. Many professional studios here are also non grounded and you can and are allowed to connect grounded equipment to non grounded outlets but not the other way around and never mix grounded and non grounded outlets in the same room.
Well it couldn’t be more different in the UK. You would unlikely have liability insurance and be, almost certainly, in breach of health and safety regulations if you were to use a non earthed mains setup in a professional setting with equipment designed to be earthed… also you would not be able to get the work certified.
Many professional studios and such like will use a TT earth system with local electrode to help reduce the noise floor.
In most domestic settings in the UK, PME (TN variant) solutions are used instead… its can allow more consistent earth leakage safety but at the expense of increased noise on the earth… that most don’t care about, and if it is important you have the option often of TT.
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This does seem rather peculiar.
If an appliance is double insulated and therefore doesn’t need a safety earth nor has an earth wire in its cable then the presence of an earth pin in the socket will make no difference, whereas, for an appliance where the case is designed to be earthed for safety, it is important that it is.
Assuming whole EU except UK has it like this? Maybe Naim is not allowed selling outside UK then 
This in Finland but similar in whole EU I believe.
Streuth 
You will find UK electrical wiring safety standards and legal requirements along with other EU countries are aligned with international standard IEC 60364 and the European CENELEC harmonisation documents.
There are apparently some local exceptions… I have no idea whether Sweden has compliance exceptions outside IEC 60364… though your description suggests they do, albeit as described could lead to some very un safe environments.
Unlike in the UK I have no Swedish chartered electricians to confer on this.
@Blackbird,…Hi,.in what part of Sweden do you live.?
I live in northern Sweden…Boden-Luleå area.
/Peder🙂
1000km south of you then 
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Thank you for all of the replies. Although it wasn’t the issue, the suggestion to add a second input to the preamp may have helped me isolate the problem.
The hum only exists when connecting the Chord GEM to the 152 XS with and a pair of Kimber Kable Hero RCA’s with WBT-0114 connectors.
If I connect the Chord GEM with a pair of cheap (Radio Shack) RCA’s I do not get a hum
Also, if I use the same Kimber Kable RCA’s and a Denon HEOS link streamer I do not get a hum.
I’m not sure why the Kimber Kable/WBT-0114 RCA’s combined with the Chord GEM are causing the hum.
They are fairly pricy RCA’s cables. Perhaps the WBT connectors aren’t compatible or maybe the Kimber RCA’s are revealing a hum that exists but cannot be heard with the cheap cables?
Anyone else have Chord/RCA connector problems or other ideas?
Thanks
On my Hugo, I found it quite difficult to get those spring loaded contacts to grip properly on the socket, so if your DAC is the same, are you sure you have a good contact on the ground connection? That’s a bit of a shot in the dark, but maybe worth checking.
Well not exactly. Earth serves a couple purposes and only when one of them is safety and the unit has a “This appliance must be earthed.” statement on the back must you do it. In Japan, unless it is a washing machine or fridge or something similar, appliances that use earth for any type of signal drain come with either a 3-2 adapter or the earth is a trailing lead off the mains plug.
In the case of Naim, it must be earthed and I paid a sparky to ensure I had earthed sockets installed. I’ll be moving to a rental accommodation for a year or two while we build a house and the Naim system will all go into storage. Several reasons for that, but one is simply there will be no mains earth and Naim requires this. I just don’t see the point in even bothering to set it up without proper earth. I’d rather buy a another hifi for 2 years that doesn’t require mains earth (so most Japanese gear) and crack out the Naim when it is in an environment to flourish.
I find that static buildup on computer systems that are not earthed is a major reliability issue. I have a 21U rack at home for work. In the previous apartment (no earth) random hangs of devices (not just computer but network appliances) was fairly frequent. Although I cannot prove that earth is the key, that is the only variable that has changed and in the current place, there are no mysterious untraceable device lockups.
Chord Qutest to SN2 via Audience Interconnect., zero noise, none nada. Could it be quality power cords, or power line conditioner, maybe.