Hi,
I agree with FvM: With the given informations it´s impossible to give useful detailed feedback.
It could be any type of amplifier for any kind of signals. It could be a bought one or a self made one.
It could be a wiring problem, a design problem, a shielding problem, a ground loop problem...
How can we know?
You have to tell us.... Type of amplifier, photos (100kBytes should be sufficient) of amplifier, and wiring... Any thing that is involved withe the "problem"
Klaus