Recently bought a SN3 and Hicap DR and have a significant hum/noise when I plug in and ground my TT. The hum is present when I select any source input, not just the phono input. I tried unplugging all other sources, including my Node X and CD player, from the SN3 and the hum/noise was still there. The hum disappears as soon as I unplug the turntable and ground.
I tried a second TT and same issue so I am fairly certain its not the TT.
Any thoughts or suggestions?
Thanks.
Try removing the HiCap. One less unknown. Is the hum volume control dependent? Sounds like a grounding issue. What turntable/cartridge? Does the hum disappear when you remove only the turntable ground? When you remove each signal cable individually or both at the same time?
Great questions. I have not removed the Hicap but will try that next. The hum increases with increase in volume and when I remove the ground it becomes even worse. I hooked up the same turntable (Thorens TD 206 and Thorens cartridge) to another integrated amp with phono stage and it works fine.
My concern is that I hear the loud hum with any source input selected. Not only with Phono selected. CD, Aux, Tuner, Stream, or AV. They all hum until I remove the single ended line inputs (RCA) or remove the TT power supply from the electrical socket.
You need to ground the system. I had the same problem but found a post on here on how to solve it.
Buy a grounding plug and any kind of shielded wire. I’m using what was left over from a garage door install. Connect one end of the wire into the plug, attaching it to just the round ground. Then connect the other end to the SN3. I loop it around the grounding post for the TT on the back of the SN3. Plug the grounding plug into your power strip or wall socket. No more hum.
Thanks @Taylormade! My critique is not to you but to Naim.
I love the sound of this amp and want to keep it. But I was not expecting to use a garage door opener wire to fix the phono stage. My $1000 UK integrated amp works fine even if there is some low level noise from the sub-par phono stage.
A bit severe… 
You have not mentioned if you have discussed your problem with your Naim dealer…? That should - always - be your first option.
Understand. I was frustrated as well. This was happening with my Norma Audio integrated as well. At that time, my dealer and Norma couldn’t solve the problem and the recommendation was to use an outboard phono stage rather than the onboard phono stage. This did make the hum go away.
When I bought the SN3, and had the same hum, I was determined to find a solution because I didn’t want to use an external phono stage.
Interestingly enough, the Nait 50 has the same issue but it’s only on the phono input. The hum does not cross into the other inputs like the SN3 or the Norma. Fortunately my solution works with the Nait 50 as well.
Sorry for the frustration but yes I have contacted them but no reply yet. Hopefully today.
This is very helpful info. Thanks.
This type of problem - of persistent hum with a Phono input - seems increasingly common. But - it doesn’t seem to happen with the sort of turntables that Naim systems were traditionally used with, in years past (such as thew Linn LP12 or Rega Planar 3, or similar).
My ‘guess’ is that turntables such as Thorens use a grounding scheme which is different. A Linn or Rega (AFAIK) have the arm grounded, back to the pre-amp. The arm is NOT grounded to the turntable. The TT is itself grounded, separately, to its incoming mains connection.
What can/does cause hum is a ground or earth loop, where there are 2 connections - which could occur is the arm is grounded to the TT chassis, rather than being floating.
YMMV, etc … as always… 
Thanks. Good to know.
Which solution was this?
Adding another separate grounding wire between the amp’s grounding post and a grounding socket as described by @Taylormade above. Hum is gone and TT sounds great!
Welcome! 
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