Speaker feedback w/PC connection

[Guest]

Archived from groups: rec.audio.tech (More info?)

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!

-Tom

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

"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.

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

Wow, thanks a lot. All I needed was the correct wording/definitions.

 

[unitron]

Archived from groups: rec.audio.tech (More info?)

"Justin Blakely \(SBC\)" <lordoeuf@sbcglobal.net> wrote in message news:<Ttnpc.48904$5u4.17782@newssvr29.news.prodigy.com>...
> Wow, thanks a lot. All I needed was the correct wording/definitions.

Be aware that the term "isolation transformer" can also, depending
on which store or company you ask for one, mean something designed to
plug into a wall socket and let you plug a TV or appliance into it to
power it properly without it actually being connected to the
electrical system. These are usually used in repair work for safety
reasons--they'll give you 120 Volts, but only 1 or 2 Amps instead of
the 15 available (or lurking, waiting for your screwdriver to slip)
from the wall socket.
So, if you say "isolation transformer" and they say "$100" or
thereabouts, that may be why.

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

"Richard Crowley" <rcrowley7@xprt.net> writes:

> 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".

Check my tutorial at
http://www.epanorama.net/documents/groundloop/index.html

> 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.
>
>

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/