Hi, I have a MP3 server in my garage I control via HTTP.  The sound
card is high end and all the MP3's I ripped myself so I know they are
also high quality.  I am routing the line level to my stereo over CAT5
and I am getting a constant buzzing sound.  I am at a loss as to how to
eliminate this problem without spending too much money.  CAT5 cable is
about 25 ft. long.

I am guessing that the best solution and possible the cheapest is just
to replace the CAT5 with plain ol' RCA cables.  However, I do not want
to invest money, get all dirty and drill more holes in my walls until I
know for certain that there are no other cost effective solutions.
Any advice is appreciated.

jg

What you have is a hum caused by a ground loop. I had the same problem
feeding my MP3's from my PC to my home theater system.

Ground loops are the most common cause of AC line frequency hum in
sound systems. Ground loops can be generally identified by a low hum
(60Hz in the US, 50Hz in Europe) through the sound system. A ground
loop in the power or video signal occurs when some components in the
same system are receiving its power from a different ground than the
other components, or the ground potential between two pieces of
equipment is not identical.

Ground loop is a common problem when connecting multiple audio-visual
system components together, there is a good change of making a nasty
ground loops. Ground loops commonly cause humming noise to audio
signals and interference bars to picture.

Audio-frequency ground loop problems are typically in the low
millivolt range, so it does not have to be much interference in
grounding system to cause problems in audio systems. 

Remember that there is no absolute ground. There is a certain amount
of resistance to electrical current between all grounding points. This
resistance can change with humidity, temperature, connected equipment
and many other variables. No matter how small, the resistance can
always allow an electrical voltage to exist across it. The ground
wires between wall sockets and power company transformers are not
perfect conductors and neither is the shield of your coaxial video
cable. If they were, ground loops would not be a problem. Effects of
ground loop in video pictures are in the form of a black shadow bar
across the screen or as tearing in the top corner of a picture. This
is caused by different earth potentials in a system.
 
An inexpensive solution to your problem would be what is called a
Ground Loop Isolator. It is easy to install at either your MP3 server
or your stereo. Don't go ripping out any cables, the cat5 will work
just fine.
 
Price: $16.99 
Brand: Radio Shack 
Catalog #: 270-054

http://www.radioshack.com/product.asp?catalog_name=CTLG&category_name=CTLG_002_001_019_008&product_id=270-054

Ray 




On 21 Jan 2005 13:30:36 -0800, "jg" <juangarcia@sacbeemail.com> wrote:

>Hi, I have a MP3 server in my garage I control via HTTP.  The sound
>card is high end and all the MP3's I ripped myself so I know they are
>also high quality.  I am routing the line level to my stereo over CAT5
>and I am getting a constant buzzing sound.  I am at a loss as to how to
>eliminate this problem without spending too much money.  CAT5 cable is
>about 25 ft. long.
>
>I am guessing that the best solution and possible the cheapest is just
>to replace the CAT5 with plain ol' RCA cables.  However, I do not want
>to invest money, get all dirty and drill more holes in my walls until I
>know for certain that there are no other cost effective solutions.
>Any advice is appreciated.
>
>jg

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On 21 Jan 2005 13:30:36 -0800, jg <juangarcia@sacbeemail.com> wrote:
> also high quality.  I am routing the line level to my stereo over CAT5
> and I am getting a constant buzzing sound.  I am at a loss as to how to
> eliminate this problem without spending too much money.  CAT5 cable is
> about 25 ft. long.

This could be caused by many different things.

I assume your stereo and your sound card both use three conductors for
line-level audio -- ground, left, and right.  If the computer does
(typical of a stereo mini-jack) but the stereo does not (usually the
outer ring of the RCA jacks are connected together inside but some,
especially on high-end equipment, is not), you will get hum.

How is the cat-5 run?  Does it go near any power lines or fluorescent
lights?  If so, you will get hum.  At the very least, avoid running
parallel to a power line within 18inches, and stay at least 24inches
from fluorescents.  When running an analog signal over cat-5 I'd
recommend doubling those numbers, and don't even cross power lines.

How did you wire the audio to the cat-5?  If you did not use a balun at
each end, cat-5 is a compromise.  Still assuming the 3-wire model, you
should use one pair (both wires in the pair) for left, another pair for
right, and both of the other pair for ground.

If you still have hum after doing all that, a balun is the best answer.

(If you do use a balun, then you use the cat-5 however it is wired, and
you still need to avoid power and fluorescent lights.)

There are other solutions than cat-5.  If a wire is easy to run, you
want shielded cable ideally with 1000ohms impedance.  But IME, RG-6
seems to work pretty well (one strand for left, another for right).

For only 25ft, maybe an FM transmitter (eg ccrane.com) would work for
you.  Or perhaps a 2.4ghz transmitter and receiver (eg x10.com).

sdb

-- 
Wanted:  Omnibook 800 & accessories, cheap, working or not
sdbuse1 on mailhost bigfoot.com

Worked like a charm.  Thank a bunch.  Just one more question.  Should I
be using a twisted pair per channel?  Do the twists affect the signal
at all?  Or would I be better off using TWO twisted pairs per channel,
thus eliminating the twist?

jg

Sylvan Butler wrote:
> On 21 Jan 2005 13:30:36 -0800, jg <juangarcia@sacbeemail.com> wrote:
> > also high quality.  I am routing the line level to my stereo over
CAT5
> > and I am getting a constant buzzing sound.  I am at a loss as to
how to
> > eliminate this problem without spending too much money.  CAT5 cable
is
> > about 25 ft. long.
>
> This could be caused by many different things.
>
> I assume your stereo and your sound card both use three conductors
for
> line-level audio -- ground, left, and right.  If the computer does
> (typical of a stereo mini-jack) but the stereo does not (usually the
> outer ring of the RCA jacks are connected together inside but some,
> especially on high-end equipment, is not), you will get hum.
>
> How is the cat-5 run?  Does it go near any power lines or fluorescent
> lights?  If so, you will get hum.  At the very least, avoid running
> parallel to a power line within 18inches, and stay at least 24inches
> from fluorescents.  When running an analog signal over cat-5 I'd
> recommend doubling those numbers, and don't even cross power lines.
>
> How did you wire the audio to the cat-5?  If you did not use a balun
at
> each end, cat-5 is a compromise.  Still assuming the 3-wire model,
you
> should use one pair (both wires in the pair) for left, another pair
for
> right, and both of the other pair for ground.
>
> If you still have hum after doing all that, a balun is the best
answer.
>
> (If you do use a balun, then you use the cat-5 however it is wired,
and
> you still need to avoid power and fluorescent lights.)
>
> There are other solutions than cat-5.  If a wire is easy to run, you
> want shielded cable ideally with 1000ohms impedance.  But IME, RG-6
> seems to work pretty well (one strand for left, another for right).
>
> For only 25ft, maybe an FM transmitter (eg ccrane.com) would work for
> you.  Or perhaps a 2.4ghz transmitter and receiver (eg x10.com).
>
> sdb
>
> --
> Wanted:  Omnibook 800 & accessories, cheap, working or not
> sdbuse1 on mailhost bigfoot.com

Out of curiousity - What worked like a charm?

The twists are there to cancel out noise use a twisted pair for each
channel.

Bob

"jg" <juangarcia@sacbeemail.com> wrote in message
news:1106505431.251251.39970@z14g2000cwz.googlegroups.com...
>
> Worked like a charm.  Thank a bunch.  Just one more question.  Should I
> be using a twisted pair per channel?  Do the twists affect the signal
> at all?  Or would I be better off using TWO twisted pairs per channel,
> thus eliminating the twist?
>
> jg
>
> Sylvan Butler wrote:
> > On 21 Jan 2005 13:30:36 -0800, jg <juangarcia@sacbeemail.com> wrote:
> > > also high quality.  I am routing the line level to my stereo over
> CAT5
> > > and I am getting a constant buzzing sound.  I am at a loss as to
> how to
> > > eliminate this problem without spending too much money.  CAT5 cable
> is
> > > about 25 ft. long.
> >
> > This could be caused by many different things.
> >
> > I assume your stereo and your sound card both use three conductors
> for
> > line-level audio -- ground, left, and right.  If the computer does
> > (typical of a stereo mini-jack) but the stereo does not (usually the
> > outer ring of the RCA jacks are connected together inside but some,
> > especially on high-end equipment, is not), you will get hum.
> >
> > How is the cat-5 run?  Does it go near any power lines or fluorescent
> > lights?  If so, you will get hum.  At the very least, avoid running
> > parallel to a power line within 18inches, and stay at least 24inches
> > from fluorescents.  When running an analog signal over cat-5 I'd
> > recommend doubling those numbers, and don't even cross power lines.
> >
> > How did you wire the audio to the cat-5?  If you did not use a balun
> at
> > each end, cat-5 is a compromise.  Still assuming the 3-wire model,
> you
> > should use one pair (both wires in the pair) for left, another pair
> for
> > right, and both of the other pair for ground.
> >
> > If you still have hum after doing all that, a balun is the best
> answer.
> >
> > (If you do use a balun, then you use the cat-5 however it is wired,
> and
> > you still need to avoid power and fluorescent lights.)
> >
> > There are other solutions than cat-5.  If a wire is easy to run, you
> > want shielded cable ideally with 1000ohms impedance.  But IME, RG-6
> > seems to work pretty well (one strand for left, another for right).
> >
> > For only 25ft, maybe an FM transmitter (eg ccrane.com) would work for
> > you.  Or perhaps a 2.4ghz transmitter and receiver (eg x10.com).
> >
> > sdb
> >
> > --
> > Wanted:  Omnibook 800 & accessories, cheap, working or not
> > sdbuse1 on mailhost bigfoot.com
>

What worked like a charm was the :Ground Loop Insulator" suggested by
Ray.  Radio Shack came through for less than $20.00

jg

Bob wrote:
> Out of curiousity - What worked like a charm?
>
> The twists are there to cancel out noise use a twisted pair for each
> channel.
>
> Bob
>
> "jg" <juangarcia@sacbeemail.com> wrote in message
> news:1106505431.251251.39970@z14g2000cwz.googlegroups.com...
> >
> > Worked like a charm.  Thank a bunch.  Just one more question.
Should I
> > be using a twisted pair per channel?  Do the twists affect the
signal
> > at all?  Or would I be better off using TWO twisted pairs per
channel,
> > thus eliminating the twist?
> >
> > jg
> >
> > Sylvan Butler wrote:
> > > On 21 Jan 2005 13:30:36 -0800, jg <juangarcia@sacbeemail.com>
wrote:
> > > > also high quality.  I am routing the line level to my stereo
over
> > CAT5
> > > > and I am getting a constant buzzing sound.  I am at a loss as
to
> > how to
> > > > eliminate this problem without spending too much money.  CAT5
cable
> > is
> > > > about 25 ft. long.
> > >
> > > This could be caused by many different things.
> > >
> > > I assume your stereo and your sound card both use three
conductors
> > for
> > > line-level audio -- ground, left, and right.  If the computer
does
> > > (typical of a stereo mini-jack) but the stereo does not (usually
the
> > > outer ring of the RCA jacks are connected together inside but
some,
> > > especially on high-end equipment, is not), you will get hum.
> > >
> > > How is the cat-5 run?  Does it go near any power lines or
fluorescent
> > > lights?  If so, you will get hum.  At the very least, avoid
running
> > > parallel to a power line within 18inches, and stay at least
24inches
> > > from fluorescents.  When running an analog signal over cat-5 I'd
> > > recommend doubling those numbers, and don't even cross power
lines.
> > >
> > > How did you wire the audio to the cat-5?  If you did not use a
balun
> > at
> > > each end, cat-5 is a compromise.  Still assuming the 3-wire
model,
> > you
> > > should use one pair (both wires in the pair) for left, another
pair
> > for
> > > right, and both of the other pair for ground.
> > >
> > > If you still have hum after doing all that, a balun is the best
> > answer.
> > >
> > > (If you do use a balun, then you use the cat-5 however it is
wired,
> > and
> > > you still need to avoid power and fluorescent lights.)
> > >
> > > There are other solutions than cat-5.  If a wire is easy to run,
you
> > > want shielded cable ideally with 1000ohms impedance.  But IME,
RG-6
> > > seems to work pretty well (one strand for left, another for
right).
> > >
> > > For only 25ft, maybe an FM transmitter (eg ccrane.com) would work
for
> > > you.  Or perhaps a 2.4ghz transmitter and receiver (eg x10.com).
> > >
> > > sdb
> > >
> > > --
> > > Wanted:  Omnibook 800 & accessories, cheap, working or not
> > > sdbuse1 on mailhost bigfoot.com
> >

The CAT5 runs underneath the house.   Other than running parallel to 2
other CAT5 cables, it does not come close to any power lines or
fluorecent lights.

As for the wiring, I wired each channel to a twisted pair.  Thus there
are still 2 more twisted pairs unused.  It would be very easy to change
that arrangement to Butler's suggestions.  However, given the Ray's
suggestion of using a Ground Loop Isolator seems to have solved the
problem I am no longer in a hurry to try it out.  I will though, but
probably not for another week or so.  I'll post the results when I do.

On Sun, 23 Jan 2005 13:57:43 -0800, Bob <bobnospam2@softhome.net> wrote:
> The twists are there to cancel out noise use a twisted pair for each
> channel.

Twists only do that for a balanced signal.  line-level audio is
unbalanced (referenced to ground) so better to use two twisted pairs per
channel, thus eliminating the twist."

There is a lot of coupling between the two wires twisted together, and
since there is no benefit to the twist with an unbalanced signal, the
twist just adds problems.

> "jg" <juangarcia@sacbeemail.com> wrote in message
> news:1106505431.251251.39970@z14g2000cwz.googlegroups.com...
>>
>> Worked like a charm.  Thank a bunch.  Just one more question.  Should I
>> be using a twisted pair per channel?  Do the twists affect the signal
>> at all?  Or would I be better off using TWO twisted pairs per channel,
>> thus eliminating the twist?

sdb
-- 
Wanted:  Omnibook 800 & accessories, cheap, working or not
sdbuse1 on mailhost bigfoot.com

On 23 Jan 2005 19:50:18 -0800, jg <juangarcia@sacbeemail.com> wrote:
> that arrangement to Butler's suggestions.  However, given the Ray's
> suggestion of using a Ground Loop Isolator seems to have solved the
> problem I am no longer in a hurry to try it out.  I will though, but
> probably not for another week or so.  I'll post the results when I do.

Don't fix what isn't broken!

(However, if you are bored, feel free to try breaking it so you have
something to fix.  :)

Using an entire pair for Left+, another for Left-, etc. may help reduce
resistive losses in the wiring, as well as reduce smearing caused by the
capacitive coupling between wires in a pair.

sdb

-- 
Wanted:  Omnibook 800 & accessories, cheap, working or not
sdbuse1 on mailhost bigfoot.com