Uniti Atom grounding switch


I’m thinking about grounding switch on the back of Uniti Atom. It is labeled “default” and “floating”. Support page says, that “If you are using the Uniti Atom connected to a mains grounded CD Player, the Uniti Atom Grounding Switch should be set to Floating”.

I assume it is related not only to CD player, but to all other sources which are connected to Uniti through RCA or any of the digital inputs, because CD player can be connected to all of them.

I do not use CD player, but I have TV connected to Uniti Atom through HDMI. And also I have wired network cable connected to Uniti (network cable comes from Asus router). What grounding position (“default” or “floating”) should I use for best quality?

And also, what grounding position should be used, if only wired network cable is plugged to Uniti and HDMI is disconnected. And vice versa, if only HDMI is plugged and network cable disconnected?

All you list - Tv, ethernet & HDMI - do not connect the Naim -ve signal circuit to ground, so you need to have the switch set to default.

I think Mike is correct, you only need to set it to ‘floating’ if a regular hifi source is connected.
If you have it set incorrectly, it will do no harm. It may cause a small reduction in sound quality, but if there is no audible difference, don’t worry about it.

Naim preamps Ned one and only one ground connection. So if all your sources are floating, then the setting is default. Traditionally Naim CD players have been signal grounded, so if you have one of these then setting is float (remember the must not be more one signal ground connection, or induced earth loops can occur)
Now the challenge is knowing with non Naim sources what they are.
So to determine you will need a resistance meter or continuity checker. Unplug the source from the mains supply, leave it for 10 minutes or so, then measure the resistance between the mains earth pin and the negative signal output (often coloured black). If the resistance is nil or one one or two ohms then that source is signal earth grounded, so treat like a Naim CD player. Otherwise assume the source signal ground is floating

Not exactly correct, not all ‘regular’ hifi has an earth in the power supply so cannot be grounded.
The Naim pre-amp analogue input requires one -ve to ground connection, more than one ground can result in ground loop noise. The switch is a means of disconnecting the amps internal analogue -ve connection to ground if another component carries an analogue signal ground (earth) connection.
The -ve circuit on Naim is part of the analogue signal circuit.
Ethernet & HDMI are digital & are connected into the DAC.
TV can be both, a pair of RCA’s connections means its analogue but I have never seen a modern TV with an earth in the power supply so it cannot carry a ground, other TV connection types will be digital.

But in my situation network cable goes to router. And this router has another cable connected which goes to computer. And computer is grounded :). So the final source input seems to be grounded.

Did you follow my suggestion to confirm whether your source is signal ground earthed?
If so what was the outcome? You previous post to Mike uses the word ‘seems’ which suggests you perhaps still don’t know.

Are these quality differences concerned only to “noise” or “hum” issues? Or maybe other problems can arise, like reduced dynamics, less punchy bass, muddy sound, cut off high frequencies, etc…?

No - the Naim ground that is relevant is the Naim pre-amp’s analogue signal ground.

I do not have resistance meter at the moment. I’ll borrow it and certainly try your suggestion later.

Cool… that way you can be sure… a simple continuity meter can also help… often a few pounds from your nearest car parts store.

To be honest, on my Atom, I can’t tell any difference. Like you, I have HDMI and Ethernet, but no HiFi boxes connected to the analogue inputs.
On my NDX/282, I can sometimes hear an extremely faint background hiss if I set it to floating, but it is so hard to tell the difference that I wouldn’t really notice it in normal listening.

Thanks. So only analog (RCA) inputs can be grounded? And all other (optical, digital, HDMI, ethernet) can’t?

Support page does not mention that CD player is Naim‘s CD player. Yes, Naim’s CD player has only analog outputs, but some other manufacturers produce CD players which in addition has digital outputs, but as I understood these digital outputs can’t be grounded?

Yes only the Naim pre-amp analogue inputs on DIN or RCA need this one ground.
You seem to be using “can’t” be grounded, there is no can or can’t in this, just it is grounded or is not grounded.

You mention Naim CD players, these always have the -ve grounded. So if you do have a Naim CDP connected, then the switch needs to be set to ‘floating’ so as to maintain just the one ground. If nothing is connected to an analogue input, or if what is connected does not have its signal -ve circuit grounded, then the switch is set to ‘default’
Ethernet, HDMI, optical etc are not connected to the pre-amp analogue inputs. So if that’s all you have connected, set to default.


I have my Nova connected to a nap 250DR - I have the switch set to default but should it be set to floating? Help appreciated

No. It’s only relevant to analogue inputs.


Good question. It very much depends what is connected to your Nova if anything. If nothing is connected or any source connected is floating, then you should set switch ‘chassis ground/default’ or equivalent. If you have a signal grounded source, and by default Naim CD players are such signal grounded sources, then you should set the switch to ‘floating’
I hope that makes sense.

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