Look at this:
Massive sudden hum - frightening! - #15 by james_n
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.
Did I f#+k up??
I unscrewed this plug, and now I can not screw it back in. Should I have squeezed the wire between this screw and plug? I can not feel anything in that hole to tighten it back any more. I am stressed out now.
Yes, I’m not sure how you unscrewed the whole thing ?
The knurled knob (at the bottom of your picture) is what you needed to unscrew. There should be an internal insulating washer, ring terminal and nut inside which looks to have come off.
I suggest getting your dealer to open up the SN3 and put it back on.
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Now I feel dumb. But thanks, i think you are right. I saw a picture here without that knurled knob and screw so i thought both needed to come off. I provisionally managed to attach the wire. Hum is gone, now it is only a soft buzz. But I will go to the dealer for repair and a permanent solution. Not my day today
It should be a nice quick job for the dealer to sort out putting the ground post back and as you say, they can then make you up a more permanent solution for the ground wire 
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Hi, new to the forum as I only just received my new SN3 with Chord M Scaler and TT2 combination. They sounded amazing at the dealer, but I was hugely disappointed last night when I’d removed my old Linn system, cabled in all the above, turned it on, and buzzing came out of the speakers.
I tried it all. Moving the TT2 1 metre from the SN3. No joy.
Swap the M Scaler and TT2 PSU’s. Still there. Unplug the RCA cables to SN3. Solved, but useless.
Disconnect the TT2 from its PSU, also resolved the buzz. Interestingly just by bringing the power connector close to the TT2 the SN3 would buzz through the speakers. The TT2 didn’t even need to be plugged in! At this stage the TT2 was going back to the dealer.
I then hooked up the TT2 to my old Linn. Nothing but silence.
I went to bed confused.
This morning I Googled, and found this thread. I stripped an old cable and using the suggestions above, threaded it around a DIN port and the Ground connector. The Supernait buzz is no more.
I just wanted to thank all the contributors on this forum for their excellent support!
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