Desk fan interferes with amplifier's right channel

[markiemrboo]

Here's an odd one.

My friend bought the same amp as me, Cambridge Audio A5, to replace his Logitech computer speakers. He's really impressed with it.... BUT:

He has a desk fan pretty much on the other side of his room to his amp. When he turns the fan on, the right channel on the amp gets this horrible low frequency buzzing noise, clearly audible over music. This only happens when he turns the fan on, it doesn't disappear when he turns the fan off. It doesn't disappear if the amp is turned off. It will only disappear if you nudge the balance knob on the amp back and forth a tiny little bit, multiple times. Then it's fine again until the fan gets turned back on!

It's really quite amazingly strange. Any idea's what might be causing this?

EDIT: Forgot to add, turning the volume all the way down so no music can be heard... this strange humming is still there.

[arneson]

Look around the room for lights on the same circuit as the fan.
Pay attention to flourecent, high intensity, and mood lights.
Turn on amp, turn on fan, start turning off lights.

This is just one of many possible things.

[markiemrboo]

He says there's no lights plugged in to the same socket as the fan. Try turning off..... anything, one at a time?

[japlytic]

The most likely fix for this problem is to install a heavy duty line filter on the fan, and then on the amplifier if the filter on the fan alone does not fix this problem.

[arneson]

I've seen corrosion in outlets do this kind of thing.
Also a fire risk from aluminum wire in house?