I got my XPS (DR) however.........

A dedicated radial circuit won't fix hum unless it's being caused in your own home - in which case you can cure it better by removing the offending equipment.

The problem is that if the offending equipment happens to be a Naim amp or power supply you lose your music 

In that case it'll also affect a dedicated radial circuit just the same.
A radial circuit isn't a magic humbuster or a silver bullet.

Chris Dolan posted:

GraemeH posted:

I've owned 3 Hicap DR's. One hummed and two didn't.

...... but did they tap their feet instead? 

Ha!

G

Alan Willby posted:

Worst identifiable offender was my wife's hairdryer by a country mile. Other moments seemed to be unconnected to appliances such as fridge, boiler, etc. use / switch cycles.

Some more basic hair dryer designs are notorious for asymmetric mains loading, causing a DC offset, and ultimately causing efficient transformers to saturate and clip and therefore loudly hum or buzz. Often the half heat setting works by taking current from just one side of the mains cycle as this is very easy and cheap to implement and thereby creating the mains offset.

Alan Willby posted:

As it happens my experience is that the DR models (SC, XPS and 250 in my case) have all been less prone to hum than their predecessors. Still had their moments though. Worst identifiable offender was my wife's hairdryer by a country mile. Other moments seemed to be unconnected to appliances such as fridge, boiler, etc. use / switch cycles.

You seem to have pretty well ID'd that you have a real problem with the other units with variable hum.   Plus "Other moments seemed to be unconnected to appliances such as fridge, boiler, etc. use / switch cycles."  None of the appliances you list have half wave speed controls these days & any speed controls are a bit more sophisticated.   It probably means the problem is coming from your local (neighbourhood) supply & in this case I agree with Huge that a dedicated radial is not going to do much.  However it will be worthwhile explaining the problem to your electrician & ask him to assess your installation from incoming main to the CU.  He might be aware of nearby installations,  farms, industrial units etc on the same supply line (not much comfort or solution for you other than there is a reason)   

Mike-B is absolutely correct.

My home network is in a similar position - due to certain limitations is shares one of the phases with some heating pumps in the basement. Occasionally (there is no pattern though) those would cause a certain assymetry / distrotion in the power supply, which feeds back to my dedicated circuits and manifests itself as a slight hum from transformers. (at least that is how I understood the explamation - if I twisted some facts, that's becasue I know nothing about electricity ).

Adam

My HiCap DR hums but my XPS and the power supplies to my 300 and 252 are silent. Can't hear anything when playing music though so just put it down to quirkiness .....

Regards,

Just as a by-the-by, I have a non-Naim "XPS", and that is guilty of being the biggest hummer in my set-up.    It's not exclusively a Naim phenomenon.

My Nap300 hummed way too much - enough that it shook. Had to ship it back to Naim, and they replaced the transformer. 0 hum after that.

I did try the Isotek Synchro trick, but that did nothing.

To test whether it's really related to smps, just switch everything else in the house off from the mains panel - everything except the line to the system. If the system still hums, getting an synchro won't  help. Neither will a dedicated circuit.