Sonos Port and Naim Supernait

Try grounding the Port.

Grab a spare RCA lead and insert it into an unused jack on the Port. (You could use a Line-In jack or even the S/PDIF coax.)

Carefully ground the shield at the other end of the cable -- without touching the centre pin on anything metallic -- and see if the hum goes away. If it does you can contemplate a more permanent arrangement.

Thanks will give it a try and report back

FWIW I just found this in a manual:

4.10 General Connections Notes

The SUPERNAIT 3 negative input and output connections for each channel are common. The mains earth (ground) should always be connected regardless of what other equipment is used in conjunction with the amplifier. The mains earth only grounds the case and the electrostatic screen within the transformer, and is not connected to the signal negative. In order to avoid hum loops, the signal negative of the whole system should be connected to the mains earth (ground) in one place.

A signal ground connection is fitted to the SUPERNAIT 3 rear panel. This is intended to be used to connect a turntable pick-up arm signal earth only.

So quick fix with a cheap piece of wire as recommended on the Naim forums fixed it

(Pic doesn’t clearly show the wire was stripped obviously - but it was 🤨)

Connect (any) outer shield of a din plug to the turntable ground and this cleared it 

will work on a more “professional” bodge later

thanks for the replies