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RCA Cable - Long Run - Isolation Question

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February 8, 2005 11:49:34 AM

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

I'll be installing a new subwoofer that works best if it's looped
in-between the amp and pre-amp, via the line in/out's. The run will be
no less than 15'. With an RCA run that long, I'm obviously concerned
about RF interference, ground loops and the like. I'll be using heavy
gage Monster Cable, which is THX certified (if that means anything).

My question is; what addition steps can I take to insure a clean,
secure, well isolated connection?

Thanks,

A_C
February 8, 2005 12:37:02 PM

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

>Not sure I follow the routing, do you mean the sub is powered?

Yes, it's an Infinity IL20a.

>What may be an issue will be whether your kit all has
>a common earth, and how well designed it is.

Which leads me to a follow-up question... If I'm powering this system
off of a non-grounded outlet, can I fashion an effective ground by
connecting the 3rd wire to a water pipe, or heating pipe? (if yes,
which would be better?).

Thanks again,

A_C
Anonymous
February 8, 2005 3:14:51 PM

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

Agent_C <Agent-C-hates-spam@nyc.rr.com> wrote:
>I'll be installing a new subwoofer that works best if it's looped
>in-between the amp and pre-amp, via the line in/out's. The run will be
>no less than 15'. With an RCA run that long, I'm obviously concerned
>about RF interference, ground loops and the like. I'll be using heavy
>gage Monster Cable, which is THX certified (if that means anything).

Cable gauge means nothing for a line-level signal where the current is
minimal. Monster Cable is for the most part overpriced junk, and you
might be better off with a better quality cable from another source
(like Canare). It will certainly cost less.

>My question is; what addition steps can I take to insure a clean,
>secure, well isolated connection?

Your main problem is going to be ground loops because you are running a
long unbalanced connection. It will help if you use the same outlet
that your amp is plugged into for the sub because it will reduce the
area of the loop a little. Try it and see how bad the problems are.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Related resources
February 8, 2005 3:16:57 PM

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

Thanks... Glad I asked!

A_C
February 8, 2005 3:16:58 PM

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

Thanks... Glad I asked!

A_C
Anonymous
February 8, 2005 3:41:14 PM

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

Agent_C <Agent-C-hates-spam@nyc.rr.com> wrote:
>
>Which leads me to a follow-up question... If I'm powering this system
>off of a non-grounded outlet, can I fashion an effective ground by
>connecting the 3rd wire to a water pipe, or heating pipe? (if yes,
>which would be better?).

No. Do not do this.

You can use a GFI if you want to operate 3-pin stuff off of a non-grounded
outlet. That is legal and meets code, which improvised water pipe grounds
do not.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
February 8, 2005 6:41:51 PM

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

In article <1107881374.658891.157840@c13g2000cwb.googlegroups.com> Agent-C-hates-spam@nyc.rr.com writes:

> I'll be installing a new subwoofer that works best if it's looped
> in-between the amp and pre-amp, via the line in/out's. The run will be
> no less than 15'. With an RCA run that long, I'm obviously concerned
> about RF interference, ground loops and the like. I'll be using heavy
> gage Monster Cable, which is THX certified (if that means anything).
>
> My question is; what addition steps can I take to insure a clean,
> secure, well isolated connection?

If it doesn't work fine with a 15 foot run, there won't be much you
can do to make it better other than redesign the equipment. If you
were taking about 100 feet, there are some things you could do, but 15
feet is a no brainer.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
February 8, 2005 7:31:57 PM

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

"Agent_C" <Agent-C-hates-spam@nyc.rr.com> wrote in message
news:1107881374.658891.157840@c13g2000cwb.googlegroups.com...
> I'll be installing a new subwoofer that works best if it's looped
> in-between the amp and pre-amp, via the line in/out's. The run will be
> no less than 15'. With an RCA run that long, I'm obviously concerned
> about RF interference, ground loops and the like. I'll be using heavy
> gage Monster Cable, which is THX certified (if that means anything).
>
> My question is; what addition steps can I take to insure a clean,
> secure, well isolated connection?
>

You should be fine. If you hear a problem, come back.

jb
Anonymous
February 8, 2005 8:14:40 PM

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

Agent_C wrote:
> I'll be installing a new subwoofer that works best if it's looped
> in-between the amp and pre-amp, via the line in/out's. The run will be
> no less than 15'. With an RCA run that long, I'm obviously concerned
> about RF interference, ground loops and the like. I'll be using heavy
> gage Monster Cable, which is THX certified (if that means anything).
>
> My question is; what addition steps can I take to insure a clean,
> secure, well isolated connection?
>
> Thanks,
>
> A_C
>
Not sure I follow the routing, do you mean the sub is powered?

Unless you have anything nasty around, 15' of unbalanced audio will
probably be OK. Hum loops may be a problem but the length is not going
to be the cause. What may be an issue will be whether your kit all has
a common earth, and how well designed it is.

THX and "heavy gauge Monster cable", just means that you have, in all
probability, paid too much for it. Sorry, but I smell Snake Oil.
Anonymous
February 8, 2005 8:14:41 PM

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

On Tue, 08 Feb 2005 17:14:40 +0000, Andrew Chesters <andrew.dontspam.chesters@ntlworld.com> wrote:
>Agent_C wrote:
>> I'll be installing a new subwoofer that works best if it's looped
>> in-between the amp and pre-amp, via the line in/out's. The run will be
>> no less than 15'. With an RCA run that long, I'm obviously concerned
>> about RF interference, ground loops and the like. I'll be using heavy
>> gage Monster Cable, which is THX certified (if that means anything).
>>
>> My question is; what addition steps can I take to insure a clean,
>> secure, well isolated connection?
>>
>> Thanks,
>>
>> A_C
>>
>Not sure I follow the routing, do you mean the sub is powered?

>Unless you have anything nasty around, 15' of unbalanced audio will
>probably be OK. Hum loops may be a problem but the length is not going
>to be the cause. What may be an issue will be whether your kit all has
>a common earth, and how well designed it is.

>THX and "heavy gauge Monster cable", just means that you have, in all
>probability, paid too much for it. Sorry, but I smell Snake Oil.

15' of monster cable isn't going to work as well as 15' of microphone
cable. The problem with monster is that they've bought into the pseudo-
balanced cable nonsense and their cables only have the shield connected
at one end. All that accomplishes on unbalanced equipment is reduced
shielding. I guess they have to come up with something to help
their buyers feel better about pissing their money away.
Anonymous
February 8, 2005 8:50:52 PM

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

Agent_C wrote:
>>Not sure I follow the routing, do you mean the sub is powered?
>
>
> Yes, it's an Infinity IL20a.
>
>
>>What may be an issue will be whether your kit all has
>>a common earth, and how well designed it is.
>
>
> Which leads me to a follow-up question... If I'm powering this system
> off of a non-grounded outlet, can I fashion an effective ground by
> connecting the 3rd wire to a water pipe, or heating pipe? (if yes,
> which would be better?).
>
> Thanks again,
>
> A_C
>
In the civilized world, ALL outlets are grounded!! If your kit neads
grounding, and you outlets don't provide it, get proffesional advice.
Don't endanger yourself, or others, please!
If the kit is designed to be ungrounded, you may be less likely to
suffer hum loops.
Anonymous
February 8, 2005 9:53:56 PM

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

In article <1107884222.197299.59820@z14g2000cwz.googlegroups.com>,
Agent_C <Agent-C-hates-spam@nyc.rr.com> wrote:

>Which leads me to a follow-up question... If I'm powering this system
>off of a non-grounded outlet, can I fashion an effective ground by
>connecting the 3rd wire to a water pipe, or heating pipe? (if yes,
>which would be better?).

Electrically, connecting to one of these pipes may work, or may not
work - it'll depend on how your building is piped.

Legally, it's very probably a violation of your local electrical and
building codes (which are probably based on the National Electric
Code) to do this.

The reason has to do with safety. If you ground your system to a
water pipe, and a hot-to-ground short circuit should occur, your water
pipes can then become "live", and be lifted to quite a few volts above
building-ground voltage because their resistance isn't zero. This can
create a shock hazard for people elsewhere in the building. If, for
example, you ground to a cold-water pipe, and it goes "live" due to a
short, and someone elsewhere in the building is touching both the cold
and hot water pipes (or faucets, or etc.) then their body can become
part of the short circuit's path to ground and can carry a significant
current. Since it doesn't require more than a few milliamperes of
current through the torso to interfere with the heart, the results
could be Bad.

It is similarly a code violation to connect the ground and neutral
pins of an outlet together. Neutral is allowed to carry a current
during normal operation, but the safety ground is supposed to be on a
current-free wire of its own, and be returned directly to the ground
bus at the breaker panel.

The only legal way I know of to install a three-prong outlet on a
two-wire circuit, without having to run a new ground line back to the
breaker box, is to use an outlet equipped with a ground-fault
interruptor. This doesn't provide an actual earth ground to the third
pin, but it does provide shock protection. I don't see that doing
this would help (or hurt) the performance of an audio amplifier.

--
Dave Platt <dplatt@radagast.org> AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
Anonymous
February 8, 2005 9:53:57 PM

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

Dave Platt wrote:

> In article <1107884222.197299.59820@z14g2000cwz.googlegroups.com>,
> Agent_C <Agent-C-hates-spam@nyc.rr.com> wrote:
>
> >Which leads me to a follow-up question... If I'm powering this system
> >off of a non-grounded outlet, can I fashion an effective ground by
> >connecting the 3rd wire to a water pipe, or heating pipe? (if yes,
> >which would be better?).
>
> Electrically, connecting to one of these pipes may work, or may not
> work - it'll depend on how your building is piped.
>
> Legally, it's very probably a violation of your local electrical and
> building codes (which are probably based on the National Electric
> Code) to do this.
>
> The reason has to do with safety. If you ground your system to a
> water pipe, and a hot-to-ground short circuit should occur, your water
> pipes can then become "live", and be lifted to quite a few volts above
> building-ground voltage because their resistance isn't zero. This can
> create a shock hazard for people elsewhere in the building. If, for
> example, you ground to a cold-water pipe, and it goes "live" due to a
> short, and someone elsewhere in the building is touching both the cold
> and hot water pipes (or faucets, or etc.) then their body can become
> part of the short circuit's path to ground and can carry a significant
> current. Since it doesn't require more than a few milliamperes of
> current through the torso to interfere with the heart, the results
> could be Bad.
>
> It is similarly a code violation to connect the ground and neutral
> pins of an outlet together. Neutral is allowed to carry a current
> during normal operation, but the safety ground is supposed to be on a
> current-free wire of its own, and be returned directly to the ground
> bus at the breaker panel.
>
> The only legal way I know of to install a three-prong outlet on a
> two-wire circuit, without having to run a new ground line back to the
> breaker box, is to use an outlet equipped with a ground-fault
> interruptor. This doesn't provide an actual earth ground to the third
> pin, but it does provide shock protection. I don't see that doing
> this would help (or hurt) the performance of an audio amplifier.
>
> --
> Dave Platt <dplatt@radagast.org> AE6EO
> Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
> I do _not_ wish to receive unsolicited commercial email, and I will
> boycott any company which has the gall to send me such ads!

Keep in mind what ground really is. In the United States, the neutral
and ground are tied together in the electrical service box. This service box
neutral/ground is then bonded to a ground rod or water pipe to effect the
ground. In a 3 wire system, the ground is a non current carrying conductor.
Its at the same potential as the neutral with no load on the outlet. Its
basically there for safety reasons.
Externally grounding the units will not solve a ground loop problem. A
ground loop is when two units have dissimilar grounds and current flows
through the signal connectors shield from one unit to another. This induces
noise in the audio lines. The best way to help avoid this is the plug into
the same outlet or on the same breaker if possible.

Now, why the loop through? Are you using the subwoofer as
a high pass filter for you satellite speakers? Keep in mind if you
loop through the line level, a disturbance or power down in the powered sub
may cause noise in the mains.

What would i do? Buy good cables. Only as long as are needed.
Try to power from the same electrical outlet or breaker. Then see
what happens. If you really do have a grounding problem, transformers or so
form of ground isolation may be needed between the two units to isolate the
grounds.

Bob



----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
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Anonymous
February 8, 2005 10:23:34 PM

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

Dave Platt wrote:
>
> The reason has to do with safety. If you ground your system to a
> water pipe, and a hot-to-ground short circuit should occur, your water
> pipes can then become "live", and be lifted to quite a few volts above
> building-ground voltage because their resistance isn't zero. This can
> create a shock hazard for people elsewhere in the building.

....especially as you sometimes can't be sure that the water pipes
haven't been replaced (or originally built) with plastic in some part of
the building you can't see.

--
Anahata
anahata@treewind.co.uk -+- http://www.treewind.co.uk
Home: 01638 720444 Mob: 07976 263827
February 8, 2005 10:24:26 PM

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

reddred wrote:
> "Agent_C" <Agent-C-hates-spam@nyc.rr.com> wrote in message
> news:1107881374.658891.157840@c13g2000cwb.googlegroups.com...
> > I'll be installing a new subwoofer that works best if it's looped
> > in-between the amp and pre-amp, via the line in/out's. The run will
be
> > no less than 15'. With an RCA run that long, I'm obviously
concerned
> > about RF interference, ground loops and the like. I'll be using
heavy
> > gage Monster Cable, which is THX certified (if that means
anything).
> >
> > My question is; what addition steps can I take to insure a clean,
> > secure, well isolated connection?
> >
>
> You should be fine. If you hear a problem, come back.
>
> jb

Yep, what he said
especially if you plug all your stuff into the same outlet should be no
problem.

If you have a CATV cable connected to the system, you MAY get a ground
loop.

Mark
Anonymous
February 9, 2005 1:57:51 AM

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

In article <1107884222.197299.59820@z14g2000cwz.googlegroups.com>,
"Agent_C" <Agent-C-hates-spam@nyc.rr.com> wrote:

> >Not sure I follow the routing, do you mean the sub is powered?
>
> Yes, it's an Infinity IL20a.
>
> >What may be an issue will be whether your kit all has
> >a common earth, and how well designed it is.
>
> Which leads me to a follow-up question... If I'm powering this system
> off of a non-grounded outlet, can I fashion an effective ground by
> connecting the 3rd wire to a water pipe, or heating pipe? (if yes,
> which would be better?).
>
> Thanks again,
>
> A_C

Adding an odd ground would really cause serious problems. Appliances
dumping current into the outlet ground could pump a few amps through
your equipment on its way to the water pipe.

If you do have a ground loop problem, run a separate wire between the
chassis of the sub and the stereo. That will take some of the current
off the audio coax. If it still hums, add an isolation transformer to
the audio line.
February 9, 2005 12:51:05 PM

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

Yeah, all the components, including the sub, will be plugged into a 10
outlet Power Wedge. Based on what everyone's saying, I should be fine,
I guess.

Thanks,

A_C
Anonymous
February 9, 2005 3:53:26 PM

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

In article <1107919466.370656.11330@z14g2000cwz.googlegroups.com> makolber@yahoo.com writes:

> If you have a CATV cable connected to the system, you MAY get a ground
> loop.

Correction - If you have a CATV cable connected to the system, you
WILL have a ground loop. The most expensive cable Monster has won't
help you, however the cheapest 75 ohm isolation transformer you can
find will help a lot.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
!