RFI with PC speakers

[Paul]

My 2.1 speaker system "PC Works" by Cambridge Soundworks is picking up quite
a bit of RFI. It's manifested in audible whispering radio station
broadcasts. When I moved in here, RFI was very audible. So I was suggested
to put ferrite chokes around audio and power cable. I did that, and it
worked for quite a while. Recently, I've been getting loud RFIs yet again.
Now I don't know whether those ferrite chokes did anything, and not mere
rearrangement of the cables. I took them off and there seems to be no
change. RFIs come in at varying volume rates lately to the point that I
turn the amplifier off over the night as in complete silence it's quite
audible. By process of elimination I ruled out several possible causes. At
first I thought it was the computer's sound card (had that happen before
too!). I plugged headphones directly into the Lineout, silence, no RFIs.
I rearranged the audio cable but that didnt do much. I pulled the audio
cable out the amplifier. RFI is still there. So i've come to conclusion
that the amplifier is not well shielded and causes that. However, why does
intensity of RFI fluctuate? Is there anything I can do besides getting
another speaker/amp system? Ironically, I have a set of cheap speakers in
the same room on another coputer that dont have this problem! I looked
inside them, and there seems to be no shielding on them at all.

 

[Art]

You indicate that it seems to be via the amp, or maybe vis the speaker
leads?/ Have you tried relocating the amp and speaker leads, say from one
side of the room to another, just as a trouble shooting procedure? RFI can
be a real problem to diagnose and solve since even a small piece of wire
within an enclosure may react as a resonant antennea receiving the signals.
Diligence will be rewarded in finding out specifically what is the root
cause however eliminating with appropriate shielding may be difficult.
Resulting in trial and error methods to actually find a means that will
suffice, inclusive of ferrite cores, decoupling caps, etc.
"Paul" <movsw@mail.ru> wrote in message
news:QdidnUpkMuuVvjjcRVn-hQ@rcn.net...

My 2.1 speaker system "PC Works" by Cambridge Soundworks is picking up
quite a bit of RFI. It's manifested in audible whispering radio station
broadcasts. When I moved in here, RFI was very audible. So I was
suggested to put ferrite chokes around audio and power cable. I did that,
and it worked for quite a while. Recently, I've been getting loud RFIs
yet again. Now I don't know whether those ferrite chokes did anything, and
not mere rearrangement of the cables. I took them off and there seems to
be no change. RFIs come in at varying volume rates lately to the point
that I turn the amplifier off over the night as in complete silence it's
quite audible. By process of elimination I ruled out several possible
causes. At first I thought it was the computer's sound card (had that
happen before too!). I plugged headphones directly into the Lineout,
silence, no RFIs. I rearranged the audio cable but that didnt do much. I
pulled the audio cable out the amplifier. RFI is still there. So i've
come to conclusion that the amplifier is not well shielded and causes
that. However, why does intensity of RFI fluctuate? Is there anything I
can do besides getting another speaker/amp system? Ironically, I have a
set of cheap speakers in the same room on another coputer that dont have
this problem! I looked inside them, and there seems to be no shielding on
them at all.