Yes case work (chassis) will be connected to earth… almost certain,y for safety compliance as well… otherwise it would fail earth testing… It’s then a case whether signal ground floats or goes to Earth via the switch.
You can easily measure with an ohm meter.
From memory one or more of the Bundy pins are earth when you use an external PSU. There is probably a pin out somewhere. Found it… pin E
The earth from the power lead is always connected to the case, that’s the safety earth.
The floating/chassis switch is making the connection off/on earth (maybe via a resistor) for the signal circuit ground (-ve)
The point is
When the ndac is not powered with external PSU, the signal ground goes through the casework.
When upgraded with an external PSU, including the 555ps, Naim chose to NOT use the casework, but a dedicated cable.
So there is clue which might be better.
The OP’s method is very similar to what Naim use in the 555ps.
Correct that is my point… and there is a switch to couple signal ground to chassis (earth) or float. It really is very simple. At least it is with all my Naim products. An ohm meter confirms to the earth pin on the IEC socket… My DAVE signal ground is also coupled to mains earth… when I measured it was something like 0.1 or 0.05 ohms. But on DAVE you have no choice.
Even with an external PS, the nDAC still uses its own earth connection as it still has its mains cable connected. There would be no point using the mains earth connection from the XPS via the Burndy. The NDX2 (for example) will use this mains earth connection when using an external supply. You can see this connection from the Burndy socket to chsssis.
The bolt circled is the chassis connection to the ground switch.
That’s not an ndac.
When set to floating the ndac chassis ground is disconnected from the signal ground connection.
Indeed it’s an NDX2 as i said in my post. I was using the internal shot to illustrate the difference in the use of the mains earth connection carried via the Burndy from the XPS in the NDX2 compared to the nDAC which has already been explained (and you posted a picture of the nDAC in one of your earlier posts).
Yes, no one is disputing that.
I have ND5XS2, nDAC/555DR, 52, 135s.
Should I set the button on the streamer to chassis and the nDAC to floating?
Or try various combinations and use the one that sounds best!?
Jim - Assuming you have the ND5 XS2 connected to the nDAC via coax (and do not have the ND5XS2 connected its analogue DIN connection to the 52) then the nDAC switch should be set to chassis as per Naim’s recommendation.
As the nDAC is providing the signal ground / mains earth connection, the ND5XS2 switch setting can be at float or chassis – you can experiment here to see if you find any difference.
Thanks, James.
Yes, I just use a DC1.
No direct connection from streamer to 52.
Set both the ND5XS2 and the Ndac to floating.
The the signal ground will go to earth through the 555DR.
If set to floating the signal ground will not go through the Ndac mains earth connection. That is what the switch is for, either connecting or disconnecting.
No. The switch needs to be set to floating.
Yes, no one is arguing that it isn’t.
The mains lead to the nDAC provides the mains earth connection. This is connected to the chassis of the nDAC. The nDAC ground switch, when set to chassis, connects the signal ground to chassis (effectively connecting it to mains earth via the nDAC mains lead).
When you add an external PS to the nDAC, even though this PS has a mains earth connection and carries this mains earth connection via the Burndy, the nDAC doesn’t use this. It still has its own Mains power lead connected and this provides the mains earth connection. Again, if the signal ground switch is set to chassis, signal ground connects to mains earth, via the nDAC chassis and the nDAC mains lead.
Currently, I have the streamer on Floating, not Default.
And the DAC on Chassis, not Floating.
Which is correct.
Maybe this explains why I didn’t notice much improvement when I added an XPS to my original Ndac. 
Are you sure about that? The socket corresponding to “E Chassis GND” doesn’t seem to be populated in the nDAC plug, which would suggest that the local GND is used even when using a power supply upgrade. And it makes sense since the nDAC remains plugged in the mains via its own cable.
Yep - same on the HDX as both this and the nDAC still retain their own mains connection when an external PS is added.
My streamer, DAC, Supercap and 555DR are plugged in with a four headed Grahams Hydra.
My 135s use Powerlines.
Presumably that makes no difference to the grounding of the system.
