I'm not new to groud loops, I've delt with them in the past, but what is going on now Im not completely sure its a ground loop.
First a little history.
My setup is a 2 channel and in it I have a Conrad Johnson Amp. If I have the speaker wires plugged in and the amp plugged into the wall and nothing else and I turn it on I get a whine though the speakers until I connect the preamp interconnects to the amp, then the whine completely goes away. The whine isn't loud but you can hear it in the room.
Now to Yesterday.
I got my new Cambridge Audio Azur 840 XD amp. So I do the same thing, I hook up the speakers and power and nothing else and turn it on. Not a whine this time but a barely audible buzz/hum. So I hook up the preamp, first the right channel interconnect, buzz/hum goes away and its perfectly quiet, just like what happens in the CJ. Now I connect the left inteconnect - buzz/hum comes back but louder now, not super loud but there is no way one could use this in a critical listening situation. So now I take out the left interconnect, buzz/hum goes away and its quite again. Remember the right interconnect is still in so I unplug it from the amp (buzz/hum come back but its the quieter buzz/hum since both interconnects arn't in). I take the right interconnect and plug it into the left input on the amp to see if its the preamp. If I get the quite from the speakers when I do this the buzz/hum must be imminating from the left output of the preamp, but this does not happen, the louder buzz/hum comes back. So I do the same thing with the left interconnect, first the right channel input only, then the left - same results. When only in the right, its nice and quite, but in the left only buzz/hum. Of course when both are plugged in I get the buzz/hum as well.
Understand that even the louder buzz/hum is not super loud, just lout enough that it can be heard in quiet passages of the music.
This is a bridgable amp I can run mono. So with both interconnects in and the hum audible I flip the switch to mono and the hum gets louder in the right speaker. I guess something in the left channle is getting amplified and mixed in with the right channel.
So what I'm not clear on is if there any ground loop issue that can cause only one channel to this, or is it what I suspect, its the amp.
One other thing to note, when the box came to the house the whole corner was ripped open and down the edge a bit so that you coulse pull out the instruction. Now the whole amp was covered in foam and there was no apparent damage, scratches or anything, but obviously the box when through some truama getting to my house. I took pictures prior to openning it. I will be calling the company who I bought it from today to see what there thoughts are on this situtation are as well.
Any help on this would be appreciated.
So to summerize:
amp with no inputs but plugged in = quiet buzz/hum - barely audible
pre amp out right > amp right in = no hum/buzz
pre amp out left > amp left in = loud buzz/hum
pre amp out right > amp left in = loud buzz/hum
pre amp out left > amp right in = no hum/ buzz
pre amp out left/right > amp left/right in = loud buzz/hum
