Earth Loop Hum

Bryce,  Thank you for providing more detail, I can now understand why you're having so much difficulty with this.  

The key to diagnosing problems is to find the simplest setup that causes the problem, not just by switching inputs, but by disconnecting interconnect cables and unplugging units for the mains.  Take the system down to a minimum that could show the problem (poweramp, it's PSU and the speakers only), then add components to the system one at a time...

Reconnect the preamp, then add back the CD player (& PSU),

Disconnect the CD player and reconnect the TT & head amp,

Disconnect the TT & head amp; disconnect everything from the Arcam 850, and connect it to the preamp (& PSU); then, one by one, add back each of the components that connect to the receiver.

Leaving the Arcam connected, reconnect the TT & head amp,

Then reconnect the CD player (& PSU).


This should give you a clearer picture of which components are interacting.


It has occurred to me that you stated you need a long extension cable to get the Arcam and the 552 onto the same earth circuit.

How is the signal connected between these two?  If you have a long pair of phono leads this could be a problem as then you'll basically be hanging a long pair of radio antennae off the 552!  This could induce hum any time they are connected to the 552, even when the Arcam ends of the leads are disconnected.

Do these leads lie parallel and close to a mains cable at any point?
Does this apply to any other signal cables (including speaker cables)?

The problem is that this is the sort of detail that's needed to isolate these problems, and the sort of things a dealer should spot instantly as being a potential problem ; if they don't see this, change your dealer (but unfortunately a bit late now as you've bought all your kit).
(And long analogue signal leads from the A/V setup to the 2ch setup aren't exactly ideal anyway).

Clicking on the 2 links in bold should work if the photos don't automatically display.











Rega Planar 3 TT


Stageline / Control4 Base



Home Cinema



Landline / Philips Hue Tap / Control 4 Remote

Sky Q Silver / 3 Mobile Signal Booster

Arcam 850 AV Processor



Oppo 203 UHD

Lumagen Radiance Pro (Amazon Fire TV, Apple TV 4th gen both hidden)

Arcam 429 [4 channel power amplifier]

Huge - I've worked out, edited and tidied up.  Sorry if I was ranting.

Yes, I do have a long pair of phono leads, but disconnecting them at the Naim end makes the problem significantly worse.  I understand this may mean I have two issues rather than one but regardless I have a big issue confined to the 555CD/552/300.

I struggle to see how anybody can keep interconnects and mains leads apart for their entire length unless they have a simple system that's not backing onto a wall.

If you saw the shape of my room you'd probably agree that long AV interconnects was a necessary evil but I accept your comment.

And I think it was Alex who asked for a photo of the back of the Arcam 850 - too close to the wall to get a useful picture.

I ran long phono leads of 20ft from Denon AVR to 552, incorporating isolators.  No issues.

If the CD555 is all that is connected to the 552/300 and speakers, and you still have hum, your dealer will know the best next steps.

Interested to learn how this resolves.


Bryce - thanks for posting the pictures. Two things - 

1 - I'd move the 300 and stageline to the left hand rack. Move all the power supplies to the right hand rack. This will give you brain and brawn stacks (hopefully this won't cause issues with your turntable) and also allow you to dress the Burndy cables easily. A couple more shelves would give you more room and allow you to raise your turntable up a bit. 

2 - The wireless Control 4 thing on the right hand rack next to the Stageline. I'd keep wireless devices away from your Hi-Fi kit. 

Other than that it will be interesting to hear what your dealer finds. 


Update - dealer was out on Thursday and tried various things with power leads, SNAIC, interconnects including DIN - XLR without success.  He's since had several phone calls with hopefully clever people at Naim.  They suggested that the transport screws might have damaged some wiring which sounds rather like a design flaw to me!  Yesterday he was back and substituted a Moon CD player for the CD555 using existing power and IC leads.  No hum.

We've both lost track of what we've previously tried but he definitely tried a different CD555 at one point and we both thought different 555PS and brundies too so slightly confusing but feels like progress.  He is taking my CD555, 555PS and brundies back to the shop to try on a different Naim system.  Assuming the player is going back to Naim for repair I can get it serviced at the same time.  Over ten years old.

Fingers crossed and vvery grateful for all the help on the forum.

Bryce Curdy posted:

...  Assuming the player is going back to Naim for repair I can get it serviced at the same time.  Over ten years old.


That may be the reason, capacitors can go out of spec with time.

Usually they do it slowly but occasionally you get one that deteriorates faster than usual.  It's rare but it does happen and there's no way to know when the unit is built at the factory.  There's no way to test for the ones that will go out of spec sooner, it's purely random.

Dealer says he could reproduce hum (but not as loud) with a non-Naim amp in the shop.  I'm assuming this was a quicker and easier diagnostic than using a Naim amp and it wasn't the case that he couldn't reproduce with a Naim amp, but I should have asked this specific question when I spoke to him.  In any case, the CD555, 555PS and brundies are being returned to Naim.


Very, very disappointed at Naim.

CD555 and 555PS serviced and updated including (I think) 3 capacitors exchanged.  Naim were unable to replicate the humming problem,  I am just off the phone with my dealer who has not long plugged it into a 552 owned by a member of staff and the problem is very obvious.

Slightly off topic but having ordered the first Uniti Atom sold by my dealer I resisted the temptation to pass comment on the fiasco of the launch.  I have been a loyal Naim customer for nearly 25 years and feel extremely let down and unimpressed with both of my recent experiences.

In the event anyone from Naim reads this I would be grateful for some prioritisation. 

Bryce Curdy posted:


In the event anyone from Naim reads this I would be grateful for some prioritisation. 

Understand your frustration ... but I don't think your comments here are likely to reach the right people at Naim as a matter of priority!

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