Hi everyone. Here is my set up : CDP to Pre amp -> VDH d102 mkIII speical (very old cable in white color) pre to power -> Ecosse MA2 (resonablely new) Power to speaker -> QED Silver sipiral (resonablely new) pre and power amps - cambridge C75 and A75 (about 20 years old) The system was running perfetly okay with just a very small amount of hum ie. have to put my head within 1/2 meter of the speaker to hear any hum. Last night I swapped the VDH cable which was used between the pre and power with the Ecosse cable which was between CDP and Pre around. (this chage improved the sound quality of my system so I would like to make it permenant) then i noticed a much lounder hum and hisss. the hum is just about listenable at listening distance (only when no souce is playing) and i can feel the bass cone virbrating if i touch it with my hand (softly of coz). I selected different source on the pre-amp, hum level and hum sound unchanged, turned volume up and down, nothing changed, I have even swtiched off the CD player. its the same. I did some reseach on Internet and guessed the problem may be 'ground looping' . As far as I can remeber both of my old age cambridge pre and power amp (about 20 years old by now) has no earth connection to the socket (but I am not sure, I remeber chaging it from a 2 pin plug to one of those 13A british starndard plug about 10 years ago myself and I remeber there was no earth wiring to it) I am planning to earth my pre-amps's casing to the earth on my wall socket. can anyone advise how can it be done , SAFELY? Is my problem is ground looping? (I have doubt about it becuase it only shows up after swapped cable around) or could it be the VDH which seems to be famous for picking up noises?