This happened to me a while back, and it turned out that one of my ICs was touching one of the metal bars on my rack. Even though the IC was insulated, this caused a hum in that channel (odd). I also got a hum once when my pre's IC was touching my CD player's chassis. I would look very closely at how your cables are oriented to make sure they are away from these.
Why Oh Why...another
I was swapping things around, and now have a humm. Before, there was no humm. When the amp is plugged into the speakers and my IC's not connected to it, there is no humm. When I connect even one IC to the amp, I get a humm, even if the IC is not connected to anything else on the other end. If I put my finger on the unconnected end of the IC, the humm sound get a little louder.
What's up?
What's up?
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