Never heard the fan run on my 300, it rarely gets more than mildly warm.
I think I have sorted it . Switched the 555 to floating earth . Fan off . I think it’s using av input as the ground when I plug them in , ie more than one source
Mike,
Yes it does sound like you have multiple ground paths, along with your 3 wire sub connection.
I would start with the Marantz disconnected from the 552. Make sure the sub is only connected by the Yellow and Red wires (leave black disconnected) for a bridged application. Set the ND555 ground switch back to chassis.
Check all is well (no hum from sub and the fan not coming on for no reason), run it for a while then reconnect the Marantz and see how it goes.
High level sub connection to 500 or speaker terminals definitely not supported by Naim. I asked customer support and received an unequivocal ‘no’. As has been pointed out, this is because the 500 is a bridged design.
Take a low level connection from the pre.
Update, all working fine now after switching ND555 to float. No issues now
2 Likes
Sub also still connected by red and yellow only now
I love a simple solution… 
This topic was automatically closed 60 days after the last reply. New replies are no longer allowed.