Can anyone suggest a reason as to why I have a hum/buzz in my rear speakers please.

I have upgraded my Olive amps to the latest models. I now have DVD5, AV2, NAP250.2, NAP200 and NAPV145. Wilson Benesch Discovery front, Arcs at the rear.

When I attach the Arcs to the 200 I get a buzz – the equivalent sound level typical of an earth hum. However, when I attach the Discos to the 200 there is no hum. When I attach the arcs to the 250 there is no hum.

I don’t think I have any earth hum – when I switch off the AV2 through which, I understand, every is earthed then I do get earth hum through the centre and rear Arcs (but oddly not the front Discos)

I am a bit confused! Any suggestions or advice will be gratefully received,
Regards Ian,

..and the answer is - it's my speaker cable! The amp switched itself off - I guess it over heated.

Just swapped in some old 79 strand and all is ok.

I have been using my own diy cables - TNT - for over 5 years without any problems.

My cables are under the floorboards so perhaps there is a problem. Probably about time I got some NACA5. Is DNM reson a good alternative? - it will go under the carpet a little easier.

Reagds,
Ian