Need help finding cause of hum

Thanks to everyone for your comments.

Yes, Sid. I was wondering about some weird magnetic field -- but affecting only the right channel? I think I'd have noticed this before as nothing in the house has changed and I've been in close proximity to both speakers as I've moved them around over the last few years. None the less, I will try later to see if moving the amp eliminates it.

Almarg - the latter...that is, I physically moved the left and right speakers but the cables that had fed them were not moved. I was initially worried I'd damaged a driver on the right speaker. Somewhat relieved that did not appear to be the case as the hum now also came from the speaker that had been on the left. Note too - before moving the speakers themselves, I had also switched connections at the back of the amp...connected the left cable/speaker to the right channel out on the amp and the right cable/speaker to the left channel out. When I did this, the hum moved to the left.

Theo - I did wonder about some possible interaction between the amp's MAC Sound Pipe power cord and right speaker cable. The power outlet for the amp is right behind the right speaker (but there is also an outlet behind the left speaker). I moved the power cord to the outlet on the left side of the equipment. The hum stayed with the right speaker and the left speaker remained quiet. It's an integrated amp so if I'm understanding your sugggestion correctly, I don't think I can change the pre-amp/amp wiring. I will take a look at the phono-preamp connection if that is what you intended, however. The power transformer for the phono-pre is on the right side of the equipment near that right speaker...maybe it has been inadvertently moved and gotten a little too close to the speaker. I will check it out.

Newbee - Good suggestion. I will try this. I did shut down and unplug the power conditioner (though I did not disconnect the inputs to the amp from phono-pre, TT & CDP when this was done) - the hum was still there.

Thanks to all once again for taking the time to reply.

Al - Thanks for your reply. A lot to digest, but I'm thinking a ground loop isn't the cause. Wouldn't that cause hum in both channels? and at a higher volume? ALSO - I can hear the hum with only amp and speakers connected - no sources connected to the amp. Thanks again.

Al, Thanks. I will look into shorting plugs.

Dan, Hope you figure out what is going on with your system. In my case, the hum is there with the input on amp switched to CDP. I also hear it with the input at position 2 which is not occupied by any source. Finally, I can hear it with all input cables to the amp disconnected. For me, fortunately, it isn't an obstacle to listening to music. Just something that didn't seem right and which I hoped to correct, if possible. Not so easy, perhaps!