I have currently got a Naim Supernait 3 on home demo from Sevenoaks HiFi. I am looking at potentially replacing my Muscial Fidelity M6i. So far I am loving the SN3 but I have one persistent and annoying issue. Whenever I connect it to my Denon AVR X4400h using the AV bypass option I immediately get a humming noise from the front two stereo speakers. If I disconnect the Denon the hum goes. Whichever set of ports I plug the Denon into, the hum begins. Switching the AV bypass on and off does not change the issue. If I switch the input to Tuner (which I have my Rega RP8 with MC cartridge connected to) the hum actually increases in volume. I have never had this issue when using my Musical Fidelity amp - indeed, I have just hooked up the MF amp again and there is no hum issue at all. It is only when I plug the SN3 into the Denon that the hum begins. I have tried swapping plugs around, disconnecting all other related devices and so on but to no avail. It just seems the Nain and Denon don’t like each other. Has anyone got any ideas at all? Faulty amp or just an incompatibility issue?
It’s a pretty common problem when connecting AV kit to a Naim amp. A ground loop isolator between Denon and SN3 should cure the problem. Something like this will do the job
I doubt the SN3 has but I suspect there may be another path via the Rega. AV kit can be variable in grounding depending on what’s also connected to the AV receiver - DVD players, cable boxes etc. One way to see if it is a ground loop is to disconnect the Rega and reconnect the AV receiver - still got a hum ? I 'm assuming there is only the Rega TT and AV kit connected to the amp ?
Re-reading the original post, the OP mentions removing other connections and the hum remains. If this is the case it’s worth trying connecting the ground post on the SN3 to mains earth By making up a suitable cable and see if this stops the hum. A few things to try anyway but slightly off putting if you’ve not had problems before with the MF amp. I hope, AV hum issues aside, the SN3 is sounding better than the MF !
I have ordered a ground loop isolator from Amazon. A quick read through reviews shows that a few people claim the isolator may cause a drop off in bass but since most of my low end as far as the AVR is concerned will be going through my sub I am hoping this will not be a problem. Does it matter where the isolator is placed? AVR end or SN3 end?
Aside from this issue, I am enjoying the SN3 greatly. When I first hooked it up it sounded very, very harsh but I have left it running in the background for a few days and that harshness has now gone to be replaced with a beautifully detailed, well rounded, punchy sound. Think my MF may be up for sale if I can resolve the hum issue
Does anyone think a DIN connection would help matters?
I am sorry to disappoint you by saying this,but the ground loop Isolator devices not only isolate the hum but a great amount of low frequencies (bass) as well.
Trust me I tried one two years ago & I wouldn’t suggested it as the solution.
A ground loop isolator may well fix the hum, but I suspect the root cause is that nothing is linking signal ground to mains ground - the Aria looks to be double insulated too. Naim’s design philosophy ties signal and chassis ground in one place only, traditionally in one of the source components. (In my system, that’s the CD player, and the other Naim source box is set to floating.) @james_n‘s suggestion to make up a lead to connect the earth pin on a 13A plug to the SN3 chassis ground should fix this - BUT you should only do this if you know your way round a 13A plug! If in doubt, don’t…
Hello, I have the same problem with a NAD T758 and my Supernait2.
I tried many think but I always have the noise in the two speaker.
I have separated both, Now I have two pairs of speakers, one for HiFI and one for home theater.
I received the ground loop isolator yesterday and tried hooking it up to both the Denon end and the SN3 end. Sadly the hum persists but no problem - I can return the isolator.
I spoke with a Naim technician this morning and he confirmed it is a ground loop hum and that I should try running a copper cable from the ground socket on the rear of the SN3 to the RCA jack on the rear of the Denon where the SM3 plugs into. Will try giving this a go later.
Hello xfilian, can you give more precision where you have to connect the cable on the rear of the Denon.
Is it on the ground of the RCA plug ? on both plug ? Thank you.
A shame about the isolator but at least it seems that a ground loop isn’t your problem. I’m not quite clear what adding the additional wire will do. From what you’ve described it’s adding an additional signal ground path that is already there between the two units via the interconnect.
If that doesn’t sort out the hum then try the SN3 ground terminal to mains earth connection. Here is one I made a while back to fix a similar issue between a Sonos connect and my Nait 1.
James - perfect sir. Wired up the plug as you have above and placed the end on the ground on the SN3. Hum instantly gone. Now screwed in place and enjoying the amp with a quiet background. Thank you and everyone else who contributed.
I took the time to do the test, but unfortunately now I know what is a real HUM and I hear it when I plug the ground on my SN2 or on the NAD T758 v3.
So, what I hear is not a HUM but it is a sizzle only when I switch on the AV button.
Have you an idea what happen?
. Now do I get a new one or beat them down on price on their demo unit?? 
and I hear it when I plug the ground on my SN2 or on the NAD T758 v3.