Question about ground position for nd555

Will be installing a new to me ND555 later today. Wondering where the ground position switch should be set. I have two sources going into my 552; the new ND555, and I also have the left and right channels for my multichannel AV set up going in from the pre-out of my AV receiver into a unity gain input on the 552 via a chord clearway cable, which allows me to use the Naim set up and speakers as the left and right channels for my AV set up. Works great. All devices are powered via the same wire mold power strip, including the AV receiver.

My understanding is when there is more than one source attached to the 552, one of them should be designated as the main ground. Since I have no way of making the receiver a floating ground, I assume I have to do that at the ND555? Or have a completely misunderstood everything? Any guidance would be appreciated…

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Start with the ND555 at the default (chassis) setting. If any hum issues then try floating.

This is quite easy… may be on a FAQ somewhere, but is often asked, so you are not alone. :grinning:

The Naim NACs for optimum performance require one and only one earth grounded source component. Traditionally in the Naim world this has been the CD player.

Therefore if you have a Naim CDP connected to the NAC, then no other source should be earth grounded… so the ground switch on the ND555 set to float.

If you don’t have a Naim CDP connected, then you should set the ND555 ground switch to chassis.( assuming you have no other Naim source set to chassis connected)

If you have non Naim sources… you will need to measure… when unplugged if its mains earth pin is zero resistance to its signal ground, then it’s like a Naim CDP and is earth grounded… so you should set your ND555 ground switch to float.

Mis settings can result in hum, but often not necessarily so. It’s best to get right, as incorrect settings can add very low, possibly not directly audible noise, which can mask low level detail and presence.

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I would not assume the AV equipment has a signal ground. A lot of AV is double insulated & only has L&N power (no E earth) & as such the signal cannot be grounded.
Look at IEC plug, if it’s 2 pin, there is no earth.
Second question is even if the AV does have an E pin, how do you know the signal 0v (-ve) is grounded.
I guess it best to listen & hear if the ND is best/different in one or other positions.

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