I am having noise of 120kHz(+-10kHz) and at least the first eight harmonics in my very sensitive equipment. It's not coming in from the input (it is independent from the input and I also suppress it with approximately 180dB) The frequency also seems to low for radio transmissions. So I suspect digital noise or the power line. If I find out it is the power line (230V 50Hz), what can I plug in to clean it. Maybe something like a switched power supply with no transformation.