No interferences from router no, nothing that I can hear anyway. Router is actually in the same unit...
I used to have "hum" noises with the original tonearm (TP-25), which was "earthed" to the turntable chassis. The AT cabling (including earth) only goes to the pre amp.
What tonearm are you using?
Can you tell more (sorry if this was in previous pages) about the servicing of your Naim electronics? I wonder how much it would cost to get my Qed amps looked at, I've got a buzzing noise (regardless of audio source or volume)