Marantz 2270 Radio Frequency Interference (RFI)

[BMW rider]

Very happy owner here of a relatively new to me Marantz 2270. When listening via headphones, I can faintly hear a radio station in the background during quiet passages (streaming digital music from my network attached server). Changing the tuner dial has no effect, it's there regardless. The receiver also picks up interference from my Apple Airport Express located on the shelf beneath it; again very faint, but perceptible when on headphones. Any suggestions on how to better shield this gem of a receiver from RFI?

 

[hirscwi]

Are you located near a transmitter? Do you have the metal case on the 2270 (sorry for the dumb question). Might try reversing the wall plug.

 

[JBL GUY]

Proper RF grounding is important. It may not the same as an audio or power ground. Make sure all circuit board screws are clean and tight. Make sure all screws in the cabinet are clean and tight.

Keeping all cables as short as possible may help.

If you still have an issue after insuring all of your grounds are as good as they can be, then one of the common go to solutions are ferrite chokes on all of the cables right at the receiver.

This is to eliminate common mode RFI.

You may need to loop the cables through more than once or you may need more than one.

What are you using for an FM antenna. Even though your receiver may not be in the FM mode, RFI may come from the antenna.

The noise from your Apple Airport Express may be radiated noise that is being picked up by your receiver in the same way as the radio station. If so the ferrite chokes should help.

If the noise is being injected into the AC power line, then that is called differential mode noise and would require a good quality AC power line RFI filter. It may be doing both.

The picture below show examples of ferrite choke use.

Some have reported that when they are used on audio cables the sound is "less bright"

If your issue is annoying enough, it might turn out to be the lesser of two evils as they say.

RFI can almost always be solved, although it may be more work than you want to do.

A RF spectrum analyzer with a special type of probe (a type of low sensitivity antenna) will help to find the method of ingress.

Know any smart amateur radio operators? OK no jokes. Or commercial two-way radio shop owners?

Again this may be more effort than you want to put into this issue.

 

[BMW rider]

A few of these from Radio Shack placed on the power cable and interconnects from the DAC managed to push the noise down far enough that I'm hard pressed to hear it between tracks. Thanks for the recommendation!