An Entreq grounding box won’t help. Adding these additional items won’t fix the underlying issue. I’ll be interested in how you get on with a different phono amp.
Did you disconnect all ground wires?
Pull them all then replace one by one. If it’s a ground loop problem then it should give you an idea where the problem lies.
If not then it’s as I mentioned earlier.
That suggests that there may be a significant problem with one or more of: earth leakage, magnetic induction, capacitiative coupling to mains frequency or a PSU ripple breakthrough problem. Any of these are most likely to affect the most sensitive circuits first (i.e. the cartridge / tonearm / TT cable / Phono amp input.
Is the hum a nearly pure sine wave at 50Hz (/60Hz), or a rougher signal at 100Hz (/120Hz) indicating breakthrough of rectified ripple from a PSU?
One more thing, have you checked the phasing of the connection to the cartridge?
@Faye; is there any reason why you have not got the dealer involved, or am I missing something. These things are supposed to be simple plug & play, in your case this has not been so, you are not satisfied, the dealer gets a sizeable margin in the sale & its intended that they support the customer from this.
This is a bit ‘out there’ but worth a look. Assuming you are still using the tt built in psu…
Lift the platter on the tt and check the ground connection, unscrew it, make sure it’s clean and refit securely. Check continuity/condition of the lead.
@Xanthe Yes, phasing is totally fine.
@Mike-B Well, the only component that I got from a dealer directly, is the Atom. And as I said, it is imported, so no local support. Also, I’m not even sure that the Atom is the cause of the problem. But of course I’ll involve him, if evidence gets stronger.
@raym55 No, I’m using an external PSU. (The internal is still there though.) Also, I would like to emphasize that this probably doesn’t have anything to do with the TT’s PSU, because the hum is also audible if the turntable is completely disconnected from any PS. Just connecting the TT to the phono preamp is enough to trigger the hum.
@raym55, @Xanthe I’m really sorry, but either I’m completely wrong or we are talking at cross-purposes here. I have totally 4 sources for grounding in my chain:
2x turntable:
- the ground wire for chassis and phono (which gets connected to the preamp’s ground post)
- the ground for the motor and strobe light (which goes straight out via the power cable (3 pins!) into the power line)
1x phono preamp:
- the preamp’s ground post is connected to the power line via preamp’s power cable (3pins!). (This design is not usual to my knowlege. The phono ground should be united with the signal ground at this point and directed to the main amp (star ground!))
1x Atom:
- atom’s power cable (3pins) => ground goes to power line
Now in my case, to hear the hum (or to get any signal from the TT) both the phono-preamp and the Atom must be powered. And since their grounding is directly in the power cable (3rd pin), I’m automatically grounding them as soon as they’re connected to power. So I have no option to run these 2 devices without any grounding, right?
Then there’s the turntable:
- Whether I pull the power cable (motor’s ground!) or not, doesn’t make any difference. Hum is audible so or so.
- So the only remaining ground is the TT’s phono ground wire: And as I said, I hear a tremendous hum as soon as I disconnect it from the phono preamp. Isn’t that completely normal? Afaik, without that ground, there is no shielding afforded by all the metal parts of the turntable, so it’s obvious that this results in a tremendous hum. Please correct me if I’m mistaken.
You have an external psu and the original is still in situ…is the internal one connected in any way?
Phono cartridge or tonearm leads.
Try disconnecting cartridge leads at headshell. If its a detachable headshell it makes life easy.
Is it still the standard tonearm, if so where the wires go through the arm at the bearing end theres a small circuit board there where the leads in the arm join the leads to the phono connection.
Check there are no shorts and connections are good. Check for shorts and continuity from the headshell right through to the phono plugs.
I’m grasping at straws here, without access its all guess work.
You should have the Atom’s grounding switch set to floating.
You need to ensure that there’s no connection from the protective ground connection in the power cord to the TT to the tonearm or the phono shells.
Check to see if the TT’s tonearm and chassis are grounded via the shells of the phono cables, if they are and you use the earth wire then you have an earth loop.
If you don’t have an earth loop at the TT, then you should route the phono cables and the TT’s ground wire as closely together as possible.
You should also route the output cables from the phono amp to the Atom as closely as possible.
Preventing these type of hum problems arising from separate R&L ground connection is part of the reason Naim use DIN connectors.
Xanthe, FYI.
Faye has said the TT uses an external supply which would feed 21V DC along a pair of wires. Some of the better ones place a second regulator outside of the PSU box and it it usually located at the end of the PSU lead, fixed inside the TT. Closer to the cct it’s supplying gives better regulation and all that stuff. I have never come across a 1200 external PSU that uses 3 wires at the TT end, although that doesn’t mean they don’t exist.
The photo above shows a shielded multicore cable supplying power to the phono amp and Faye has stated that this is connected to ground.
This strongly suggests that this should be the single connection from 0V to protective ground.
Phono amp chassis to ground, not signal ground. 
What do you mean “signal ground”?
Do you mean 0V?
There should only ever be one signal ground connection… otherwise you’ll have an ‘earth loop’.
@raym55 I did those continuity checks, including those from the headshell socket to the PCB. There’s no kind of leakage.
And about the headshell: Yes, the original one is still connected by design.
And yes, there is just a pair of wires that goes from the PSU to an internal regulator as stated here:
https://www.kabusa.com/ps1200.htm
@Xanthe Setting the Atom’s switch to floating doesn’t make any difference unfortunately.
There is no connection between ground wire and power ground.
How can I measure continuity between signal shells and tonearm/chassis? Where do I place the probes? It’s the same as measuring continuity between signal shells and the ground wire, right?
As for signal ground vs chassis ground: To my knowledge there are 5 tonearm wires. One of them is black (for tonearm and chassis) and goes out via the black ground wire that gets connected to the phono preamp ground post. Green and Blue go are the signal grounds and go out via the signal cable shells to the preamp.
At the preamp the black ground wire is connected directly with the preamp’s chassis and thus, it gets grounded into the power line. The blue and green wire on the other hand continue via signal shells to the Atom.
Anyway, you’ve all been a tremendous help so far. I really feel bad taking your time much more at this point. I will make a few continuity tests, but I really think it’s best to wait for the new preamp with another grounding design than the Lehmann. Let’s see if it changes something. Will report back asap.
@Faye. Ok. I’m now at a loss as to what else to suggest but before I close I will let you know how mine is wired and maybe you will get some insight from there.
My 1200 has an external PSU and an SME tonearm (plus other bits not relevant to this discussion)
The tonearm has 2 phono leads and a ground lead which is connected to my phono amp. The phono amp is fed 24v DC via a 2 core lead by a plug in PSU. There is no phono amp connection to mains ground (earth).
The power supply is as I described earlier, with a 2 core lead with a separate 2nd regulator, feeding 21v to the TT mainboard. There is an IEC mains lead supplying the PSU.
The original PSU has been completely removed and the black round on/off switch has been bypassed. As soon as I apply power to the external PSU, the TT turns on.
There is another ground, electrically isolated from the tonearm, connected to the TT alloy top plate which then goes to a mains ground (earth) terminal. This grounds chassis and control circuits in the TT
I get no hum at all.
Hope you get this sorted. All the best.
It’s helpful to distinguish the 0V connection for the signal (also known as signal return and which is connected to the phono shells) from the protective ground which is connected to the mains ‘earth’.
With phono connections: the tonearm, the shells of the phono connectors and the shielding of the cables should be connected together and should be connected to the 0V connection of the input of the phono amp. This should also be connected to the shells of the phono output sockets, and hence connected to the 0V of the Atom. At one point only these should be connected to the mains protective ground.
If there is an additional ‘ground’ wire for the turntable, you need to establish what it’s used for. If it’s connected to the tonearm, but not connected to the phono shells, then it needs to be connected to the 0V connection at the input of the phono amp (and should be routed as close as possible to the phono cables fron the TT to the amp). If it’s connected to the tonearm AND the phono shells, it should probably be left un-connected, but the phono amp should then be configured to connect its 0V line to the mains protective earth (and the rest of the system left floating).
Dear naim community
It’s been a while.
As I said, I would report back as soon as I have my new phono preamp at hand (Clearaudio Smart Phono V2).
To my surprise the “ethernet hum” is completely gone on the new preamp. Sounds as smooth as it can be.
In comparison, on the Lehmann Black Cube the hum is still there.
I really think that it may have something to do with the different grounding design on the Lehmann, that may be causing a difference in ground potential.
What do you think?
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I’m surprised the Lehmann is causing the problem, they have a reputation of being a quality component, but if it is then it is.
Maybe worth returning if under warranty.
At least you got it fixed.
Something can still be a quality item without necessarily being compatible with every possible configuration of all other possible sets of components.
Well…I just hope that there is nothing is wrong with the Lehmann, as I had borrowed it from a friend. We’ll see.
Thank you very much for your help. I really appreciate it.