What's in a NAIM?

If the system has coax connected from the cable box or to the TV disconnect it. If it is the cause, you need a ground loop isolator.

I'm not going to rule out that the Naim might have a problem, but when video is a part of a system, it opens the door for all kinds of hum and noise. Naim is one of the most reliable and dependable brands I've ever worked with, especially their "two channel" models. It might be the Naim, but just make sure to isolate the video first.

I can confirm there is no problem with the NAIM equipment and this is HiFi only system so there is no connection to any video component - except for the DVD player that is being used only as a CD transport

I spoke with NAIM support and they confirm that their design philosophy is different from that of the consumer electronics manufacturers, which causes this problem to occur.

Grounding the neutral to the earth will fix the problem, but will it cause the source to perform differently?
- if not - why don't they ground the neutral via a three pin main plug?
- why doesn't "consumer electronics" use three pin plugs at all?
e.g. My Denon A/V Receiver only has two pins also

I have a feeling that common occurrences of bad domestic wiring led to the design decision not to ground consumer electronics, because most consumers do not posses the required knowledge or equipment to track down a bad connection/earth/neutral. Audiophiles tend to posses more knowledge in this area.

The solution offered by NAIM was to insert a stereo Ground Loop Isolation device between the DVD and the AMP.

They were not keen on employing any ad-hoc connections to either ground or neutral or between Chassis - i.e. connections not supported by way of the leads supplied with the equipment manufacturers.

These isolation devices are commonly used in disco and music amplification circles, mainly because the power supply at some venues can present problems of this nature.

Behringer has this type of product available, but it does not have phono plugs - so I might have to get creative

http://www.behringer.com/EN/Products/HD400.aspx

Having had Behringer gear for live music mixing I can confirm they are high audio quality components

Other solutions I have found are:
http://www.directproaudio.com/product.cfm?directid=55211
http://www.xitel.com/usa/prod_gli.htm
http://www.jkaudio.com/pureformer.htm

Williewonka, are you still having this problem or have you resolved it?

Grounding one of the source components - in this case the phono stage completely eliminated the hum

Thanks for all your input