Thanks for this! I’m using a Power block to do the same thing and I have contacted Chord support to flag it with them, but it seems there may need to be a fix at both ends, as other equipment seems to be able to induce hum into these amps too.
Yes, I connected the external(not both!) lead of the RCA connector to the ground on the power socked and attached this to some of the inputs of my 5si.
Actually, there are some photos of such a solution on this forum. I’ve just fixed my own instance 
So, if the wall socket has the proper ground, you can apply the double grounding which removes the buzzing.
In the past with other makes of kit I have made a common ground by connecting the metal cases or chassis together. Would this work here?
It does not work in my case. The only solution that worked for me was to connect the ground to the RCA input.
I can’t understand why other brands do not use any grounding. It is not rocket science.
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I was trying to find the photos - do you have a link to the forum post?
In the process of searching, I found this thread which makes some sense, except that without a second Naim component (beside my amp), there appears to be no signal earth point? Adding the CD player appears to provide this.
https://community.naimaudio.com/t/naim-earthing-update-please-clarify/
This is what fixed it for me: there is a grounding post on the back of the SN3.
Connect a cable between that and the earth of the power block.
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I had a really helpful call from Naim support, who suggested similar, but interestingly a support call from a Chord team member, who loves his own personal SuperNait3 suggested the following fix:
“I can confirm that taking a ground wire and running from the post on the rear panel of the Naim and then making a connection from there to underneath the cover cap for the Power Amp in socket (that is to say, making no contact to the Qutest at all), results in a dead silent amp here. No, I have no idea why.”
Care needed to avoid touching contacts, or better, affix wire with caps in place. The slightest contact cures the hum totally.
Man! The “no idea why” coming from Chord doesn’t sound very reassuring. I would give them the benefit of doubt, but still makes me wonder…
Again you’re just connecting signal ground to mains earth. The ground post on the SN is connected to signal ground. The outer of the DIN socket is effectively connected to the chassis of the SN and so to mains earth.
Yes, indeed, but a very quick and simple fix. Some thin cable with a little spring in it, connected to then earth and then sits under tension wedged nicely to the power amp in sockets. Crude, slightly ridiculous on a £3,500 amplifier, but incredibly quick / simple. It suggests to me that as this is not an exclusive problem with just one third-party device, there perhaps needs to be a permanent and elegant solution in the next generation of products?
@MMky It would not be professional for another organisation’s support team member to comment on a Naim product. He clearly knew exactly what he was doing.
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I also had the ground hum problem when connecting my Chord Qutest to the RCA input of my Supernait 3. The problem was fixed very quickly by my dealer who provided me with a link cable connecting the outer casing of a din connector to the outer case of an RCA. This used an input but provided the grounding required for the RCA. Since then I have got a chord clearway RCA to DIN cable, this has offered an alternative and more elegant solution to the problem.
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How do you do that exactly? Since I use Qutest and external powersupply, i have also that annoying hum.
What would you suggest…i have now a DIN to RCA from my SN2 to Qutest. But there is a hum. What do I need to ground with what and with which type of cable?
Make sure the ground switch is set at default (chassis) on the ND5XS2 and keep the setup you have now with the Qutest connected to the SN2. Put your existing Lavender interconnect that came with the ND5XS2 back in (ND5XS2 DIN output to one of the DIN inputs on the SN2) as well.
Does the hum go ?
Unfortunately I sold the original DIN cable so I can not try this. Is there a picture anywhere of how a single cable from ground pin to mains socket would look like? Or would it help to turn off all boxes, and reconnect and plug in again?
Here you go. No need for the mains connection as this will achieve the same. You can just wrap the bare wire around the outer of the DIN socket to try this.
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Looks simple! Just a regular single and stripped wire? (Sorry…very very non technical here)
Yep. Just screw one end under the ground post and loop the other end around the metal outer of the DIN socket. See pics here -
Cheers, I will check for a copper wire. I also have 1 spare DIN plug perhaps I can have someting more permanent made with that then.