I have a refurbished Kenwood KA-3500 amp that has worked well for three years. I recently moved apartments and in the mornings, it works as before. But starting around 5:30 pm, the amp starts buzzing with a radio station underneath the noise. Nothing affects this loud buzz, no matter the input or whether I'm using speakers or headphones. Any idea what could be causing this? Or how to stop the amp from "receiving" this station at night?
You could try moving it to a different AC outlet. Preferrably, one on a different circuit breaker. If that doesn't work, try re-arranging your cables. First, try unplugging all cables other than your speaker cables to determine if they are the source of the RF pick up.
There are several reasons for RFI, you really have to find what's causing your specific case. Try a search engine with something like"eliminating RFI from audio components".
If Jan's suggestion doesn't do it�.and going thru cable layout / setup usually DOES, than getting a set of input shorting plugs may be on the 'last resort' list.
Also, if the RFI is coming in thru the power cable(s) than an isolation transformer of sufficient capacity can help, as well.