"Justin Blakely (SBC)" wrote ...
I have a simple and I think common question:

How does one eliminate the annoying feedback heard from a stereo's
speakers
when a computer's sound card audio output is plugged into the stereo´s aux
input?
Also, there is the same but louder feedback when the antenna cable from
the
wall is plugged into the VCR (which is connected to another of the
stereo´s
aux inputs).
The phonograph, cd player, and audio deck do not cause any feedback so I
leave them plugged in. By the way, when I mean feedback, i´m refering to
the loud humming/buzzing thru the speakers. The stereo pre-amp is a
Marantz
from the mid-1970s and thus does not have any of the fancy "video" inputs.

If this question has already been asked, please excuse me. I could not
find
it logged. Thanks for any help!

From your description, I can only assume you are refering
to "hum". There are several good tutorials on eliminating
hum (caused by ground loops, etc). Google returned more
than 7000 hits for ground-loop hum. The reason you couldn't
find what you were looking for is that you were using the wrong
term. "Hum", not "feedback".

Feedback is caused by acoustic signals from speakers
traveling through the air and going back into an open
microphone. Assuming that you don't have any open
microphones in your system, it seems unlikely that your
problem is "feedback".

Ground-loop hum from cable-TV connections is a
common problem and there are vendors of isolation
transformers that break the ground loop. For example...
the "VRD-1FF Cable TV Ground Loop Isolator"
from http://www.jensentransformers.com/

Isolation transformers for audio (for your computer
connection) are also available in many places.