Power Supply Concerns and Relay Sound Issues with NDX2 and XPS

I use an NDX2 with an XPS connected to the power supply upgrade port.

For several months, due to my mistake of not properly reading the manufacturer’s manual,
I have been using both the IEC AC power of the NDX2 and the XPS simultaneously.

(When I plugged in the AC cord of the NDX, the power button LED was blinking, so I supplied power to the NDX through the XPS first and then plugged in the NDX’s AC cord.)

However, the device currently seems to be working fine without any issues.
Does the NDX2 have such protection circuit technology?
Is it possible that it might have taken any damage?

Also, after resetting the network setup of the NDX2 and turning it off and on again,
I hear the relay clicking on and off.

I have never heard this sound before, but it started happening after I reset the network setup yesterday.
However, when I switched to Server mode in this situation, the relay sound did not occur.

Currently, after supplying power to the NDX2 only through the XPS power, and rebooting,
the relay sound no longer occurs even if Server Mode is turned off.

What specific situation causes the relay sound?


The relay ‘click’ sound is quite normal. With the NDX2 is powered from the mains (no external PS) it has two internal power supplies. A very low power SMPS for standby mode, and a larger linear supply for normal operation. When you switch it out of standby, the linear supply kicks in and the SMPS turns off and this is the relay click you hear. If the NDX2 is in server mode, the linear supply stays on so no click is heard.
When you use an external PS (the XPS), the NDX2 internal power supplies are unused and there is no standby function, so the NDX2 remains permanently powered up and no relay sound will be heard.

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Its certainly not how an NDX2 (or a CDX2, which I have) is supposed to be used. Power should come ONLY from an XPS (or similar).

I cannot say if this might have caused any damage. Probably not (*), but better to ask your Naim dealer, or Naim themselves.

(* - with the Burndy Link plug removed, the NDX2’s internal PS’s will be disconnected.)