Here are a couple thoughts - they may no apply to you, Arthur, but they may help someone else someday.
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I have a friend who wires new houses for stereos, intercoms, alarms, etc. He has to make sure that no two lines carrying current cross one another, especially at a right angle. Why? because the magnetic field around one will set up a current in the other, creating some form of unwanted sound.

I used to get a hum in my stereo (living-room) when the rheostat on the dining room light was dialed. Turned out that, down in the basement, the wire to the rheostat crossed the wire going to the speaker in the kitchen.

So, Arthur, make sure no wires in your setup are crossing each other. Any kind of wire - sound, electrical, doorbell...

Another thing - don't pile excess wire into coils. I don't know why this is bad, but I have heard that we shouldn't do it.