XS3 and Topping D90SE hum in HT bypass mode

Hi, my first post here. I have been running an XS3 for nearly a year now. I use it for both stereo and HT duties to drive a pair of Q Acoustics Concept 500 speakers. The latter in combination with a Denon 3700 receiver. Up until recently I used a Bluesound Node 2i for music streaming and it all worked flawlessly. Recently I changed that to а Gustard X26 Pro DAC and a ifi Zen streamer and I started noticing a very audible hum when the XS3 was in ht bypass mode. I returned the Gustard convinced it was at fault but then the same thing happened when I connected a Topping D90SE DAC in its place. I run the XS3 off a separate power outlet as advised by the company that I bought it from and all the rest of my gear of a Belkin Pure AV power strip. I tried running the XS3 off the strip too but nothing changed.

I read up on similar issues that Naim owners have had and most pointed to an earth loop issue.

Based on the solutions I read I first tried running a piece of speaker cable connected to the XS3 ground terminal and touching that to one of the earth pins on the power strip. Nothing happened if anything the hum became stronger. It then struck me that the Node 2i used a small two prong plug (I live in Europe) while both the Gustard and the Topping had the larger Schuko type plug that has an earth connection. I then used the UK power cord that came with the XS3 with a cheap UK to EU adapter that has no earth to power the DAC and voila the hum disappeared.

My question is whether this is a half baked solution and if there is a better way to do it. The topping has a metal enclosure and I assume that that is why it has the bigger cable with the earth pin. I am not a specialist on electricity and don’t want to get electrocuted some day. Please advise…

Whatever you do, you must ensure that the NAIT XS3 is properly earthed at the mains - it’s a safety issue.

XS3 is earthed, DAC is not.

OK good. Have you tried earthing the DAC at the mains?

Don’t lift the earth on the DAC - if it’s got a metal case and a 3 pin plug then it needs to be earthed. If you just use the Nait and DAC with HT kit disconnected from the Nait do you still get hum ?

Yes still humming

You could try a ground loop isolator.

In what configuration ?

With receiver and all other gear bar the DAC disconnected.

Seen those but wouldn’t that degrade the sound quality of my chord interconnects?

With that config (no HT connected) do you still get hum if you add the additional earth wire between Nait ground post and mains earth ?

I will attempt that tomorrow and come back.

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