Hi Pierre - apart from the Nad, what else is connected to the Supernait ?
I have been through this and the difference between a “buzz” and a “hum” is either absence of any ground or a too many ground connections (ground loop), but I am darned if I can remember which way round it is. I THINK the buzz is no ground. Years ago I had the same issue with my SN1 and a Yamaha AV amp, the situation was only solved by replacing the Yamaha with a Denon. But given that you already have a Denon, that is clearly not the answer.
Have you tried grounding a spare RCA input on the Denon?
If when switching to AV on the SN3 is enabling an input with no ground, this may provide the required ground connection?
I do the tests with only the Supernait 2 and the home theater NAD 758 all other boxes out and I have the noise not a hum but a sizzle.
I plugged the power on the same electric net, on the different, I tried on a ground dedicated ( not connected to the home electric net) for the SN2 and/or the NAD and many other thing and I always have the sizzle.
Sorry it has taken a while to reply but I have been otherwise occupied.
I now have a new Supernait 3 and the demo unit has been taken back to Sevenoaks Sound and Vision. They kindly made me up an earth cable to go with my new amp as I had informed them of the humming issue. Got the new amp home, plugged it in and guess what - its as quiet as a mouse with no hum whatsoever. This is without an earth cable. A bit perplexed why one amp would produce the hum and another doesn’t but whatever - I have now have a hum-free Supernait 3 and could not be happier. Thanks again for all the advice.
Good… but odd!
Makes you wonder if there was a fault with the demo unit or it’s power cable.
Installation otherwise identical?
Yes Andy, absolutely identical. Literally unplugged the demo unit and plugged the new one in.
Oh well… I guess you’re not unhappy!
If you haven’t already, probably worth making sure Sevenoaks know the new one is unaffected, in case they want to check their demo unit. They might have lost a sale if you hadn’t persevered, and there’s an outside chance there’s a safety issue if the grounding is faulty.
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