Electromagnetic interference

Just bought a Conrad Johnson classic 2 preamp. Getting 60 cycle hum through speakers. Instructions say put the preamp well away from the amp. How far would that need to be?

There are many reasons a 60 cycle hum can occur in a system. More info about your system would be necessary to determine the issue. How far apart is the preamp and amp now? 2-3 feet?

The amp and preamp are separated by one shelf up and down. About 4 or 5 inches!
It's very simple to move the preamp away and observe the effect. As Nike says,just do it. That's your 1st step.