SN3 and AV hum

Connected my Denon AVR-X2700H up to my SN3 via RCA last week and now have a dreaded hum when using AV input. Bypass enabled and I also tried james_n’s solution of cable wrapped around a DIN socket and then attached to ground but still no joy (TT is also connected to ground).

Not sure where to go next, any suggestions gratefully received.

Try grounding the denon. The input iec for power is neutral and live only. Attach to the casework via a loosened screw.

Forgive me, I’m a complete novice at this, what do I do exactly?

If the extra ground wire is not working then it sound like you have a ground loop being created when you attach the AVR to the SN3. Try one of these between the AVR and SN3.

Out of interest what does changing the NDX2 ground switch do to the hum on the AV input ?


And in case you don’t recognise what that is;


Thanks, will order one today and see how I get on. No change when switching the ground on the NDX2 unfortunately.

Ok good to check. Give the Isolator a go :+1:

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Well to my surprise this actually made it worse. Is it a case of there are ground loop isolators and then there are ground loop isolators?

Very strange. So only occurs on the AV input, not on any other input ?

No hum with the AV receiver disconnected from the SN3 ?

Other than the AV receiver, only the LP12 and NDX2 connected ? Do you have the NDX2 earth switch set at chassis ?

Yep, hum only on AV input. If I disconnect at SN3 end the hum disappears. Only kit connected in NDX2 and LP12, nothing else. Signal ground is set to default on the NDX2.


Indeed. What cable are you using between the SN3 and AV receiver. Well away from mains cables. Can you swap in a different cable ?

Cheap RCA cable off Amazon, will see if I can buy another that’s shielded. Any you’d recommend?

I’d look for something from QED or Chord C line. I’d see if you can borrow a cable from your dealer (or at least get on sale or return if Internet based) just incase. Connecting AV to Naim kit can sometimes be a bit hit and miss so it may be a bit of trial and error here.

Aye, I had a chat with him last week and he said much the same thing and was pretty much a case of eliminating one thing at a time to see where the root cause is. The hum isn’t actually that bad but it’s there. And annoying.

I’ll order another cable off Amazon and see how it goes. Thanks for your help so far though, appreciated.

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Well at least it’s only on the AV side so it’s not affecting the music side. Still, it’s good to get to the bottom of these things and hopefully fix the issue. Report back when you get the new cable and don’t send the Isolator back just yet…

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Apologies, if you’ve already tried but have you flicked switch on the back of the NDX2 to “floating” from default?
I have same AV amplifier on av bypass to a Naim amp with no hum.
Good luck.

Ok, nailed it. Bought a shielded RCA cable and no hum! Now a happy chap. Thanks again for your help James.

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Nice one - glad you got to the bottom of it :+1:

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Does your Denon have a 2 pin European power cable with the European plug convertor fitted? Im having similar problems with a Denon AVR-X6500H humming and a kind of electrical buzzing. Its the same as you , it only happens using the AV input.

Standard UK plug. I just bought a higher quality shielded RCA cable and made sure it wasn’t touching anything - problem solved. Can’t offer you more than that I’m afraid, sorry.