I am confused when you say you can't find the cause of the ground loop.
Disconnect all inputs to the amp. Turn on amp. Noise through speakers?
yes? amp is the problem. Try a different outlet or use a conditioner. No noise? Plug in input from pre-amp (with no other connections to pre-amp). Noise? yes, pre-amp or interconnection cables are the problem. no noise? not the pre-amp or cables from pre-amp to amp.
Plug a source into pre-amp. Noise? yes? Source or interconnects from source to pre-amp the problem. no noise? plug different source and so on.
Check to see if outlet has ground connected.
some cables aren't made very well, so better cables with better shielding helps.
Also, don't run interconnect cables near power cables.
I agree with many hear that if it is a ground loop. Find the cause and fix it. masking the sound with cheaters (not ever a good idea because you actually lift the safety ground and now in the event of a fault, you, your kids, your pets, etc. become a better path to ground).
take the time to find find the problem.
enjoy
Disconnect all inputs to the amp. Turn on amp. Noise through speakers?
yes? amp is the problem. Try a different outlet or use a conditioner. No noise? Plug in input from pre-amp (with no other connections to pre-amp). Noise? yes, pre-amp or interconnection cables are the problem. no noise? not the pre-amp or cables from pre-amp to amp.
Plug a source into pre-amp. Noise? yes? Source or interconnects from source to pre-amp the problem. no noise? plug different source and so on.
Check to see if outlet has ground connected.
some cables aren't made very well, so better cables with better shielding helps.
Also, don't run interconnect cables near power cables.
I agree with many hear that if it is a ground loop. Find the cause and fix it. masking the sound with cheaters (not ever a good idea because you actually lift the safety ground and now in the event of a fault, you, your kids, your pets, etc. become a better path to ground).
take the time to find find the problem.
enjoy