A friend reports if she plugs her amp into her outdoor GFCI outlet she
gets noise, plugged into any other outlet no noise at all.

can a GFCI cause this? I dont mind replacing it, but havent seen this
trouble before. will plug my oputlet tester in to check it but the home
is recently purchased and passed home inspection, so i doubt its miss
wired

In oups.com,
wrote:
A friend reports if she plugs her amp into her outdoor GFCI outlet she
gets noise, plugged into any other outlet no noise at all.

What kind of noise - 60 cycle hum, hiss, buzz, other? Is the amp old or new?
3 prong plug?


My bet would be it's the location, not the GFCI-ness of the outlet...unless
it's ungrounded, which might be allowed in certain situations. Your tester
will tell.

I'd be loathe to plug a musical instrument or vocal amp used outside into a
circuit *not* protected by a GFCI. These things are notorious for letting a
harmful potential reach the metal case of a microphone or the pickups /
strings of an electric guitar. Not always harmful unless your feet are well
grounded --- and that's exactly what a GFCI id designed to protect against.
It measures current through the hot and neutral wires and if they are not
equal (well...opposite) some of the current is going somewhere else ---
possibly though a human body --- and stops it within 6 milliseconds.

To be fair this equipment was used outdoors long before we had GFCI's but
it's a hazard we can prevent today.

Depending on why there's noise, you could consider putting the GFCI upstream
of the outdoor outlet with wiring to the latter coming from the "load side."
All of our outdoor outlets are done that way to prevent nuisance trips
caused by wet weather.
--
Jim
"Remember, an amateur built the Ark; professionals built the Titanic."

On Sun, 30 Apr 2006 19:08:22 GMT, "Jim Nugent"
wrote:

In oups.com,
wrote:
A friend reports if she plugs her amp into her outdoor GFCI outlet she
gets noise, plugged into any other outlet no noise at all.

As an aside, I have a tv a foot from a wall switch for a ceiling
light. When I'm playing a weak tv station, and the light is on, I can
hear slight buzzing I guess you would call it from the tv along with
the regular tv sound.

No GFCI and I don't know what kind of switch it is. It doesn't spring
into place with a click. It's silent, but I didn't think it was
mercury either. Is it possible to be silent but not mercury. It was
not the cheapest switch, but only a dime or quarter more than the
cheapest. 21 years old.

One line below.

What kind of noise - 60 cycle hum, hiss, buzz, other? Is the amp old or new?
3 prong plug?


My bet would be it's the location, not the GFCI-ness of the outlet...unless
it's ungrounded, which might be allowed in certain situations. Your tester
will tell.

I'd be loathe to plug a musical instrument or vocal amp used outside into a
circuit *not* protected by a GFCI. These things are notorious for letting a
harmful potential reach the metal case of a microphone or the pickups /
strings of an electric guitar. Not always harmful unless your feet are well
grounded --- and that's exactly what a GFCI id designed to protect against.
It measures current through the hot and neutral wires and if they are not
equal (well...opposite) some of the current is going somewhere else ---
possibly though a human body --- and stops it within 6 milliseconds.

To be fair this equipment was used outdoors long before we had GFCI's but

This is why Keith Richards is in the hospital today!

it's a hazard we can prevent today.

Depending on why there's noise, you could consider putting the GFCI upstream
of the outdoor outlet with wiring to the latter coming from the "load side."
All of our outdoor outlets are done that way to prevent nuisance trips
caused by wet weather.

I beleve its a regular audio amp tied to a disc player but will check

On 30 Apr 2006 10:15:39 -0700, "
wrote:

A friend reports if she plugs her amp into her outdoor GFCI outlet she
gets noise, plugged into any other outlet no noise at all.

can a GFCI cause this? I dont mind replacing it, but havent seen this
trouble before. will plug my oputlet tester in to check it but the home
is recently purchased and passed home inspection, so i doubt its miss
wired
Not for sure ,but it sounds like a possiableground problem or the amp
is picking up some interfernce from antoher device that is on the same
circut. Try unplugging motorized devices one at a time and see if the
noise stops
Best Regards
Anthony



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"g.a.miller" wrote in message
...
On 30 Apr 2006 10:15:39 -0700, "
wrote:

A friend reports if she plugs her amp into her outdoor GFCI outlet she
gets noise, plugged into any other outlet no noise at all.

can a GFCI cause this? I dont mind replacing it, but havent seen this
trouble before. will plug my oputlet tester in to check it but the home
is recently purchased and passed home inspection, so i doubt its miss
wired
Not for sure ,but it sounds like a possiableground problem or the amp
is picking up some interfernce from antoher device that is on the same
circut. Try unplugging motorized devices one at a time and see if the
noise stops
Best Regards
Anthony


GFCIs inject a half-wave ac signal on the neutral and ground lines, in order
to detect a N-G fault downstream. This is probably causing the noise. The
solution is to use a non-GFCI receptacle for sensitive electronics.

Ben Miller

--
Benjamin D. Miller, PE
B. MILLER ENGINEERING
www.bmillerengineering.com


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"Ben Miller" wrote in message
...
The
solution is to use a non-GFCI receptacle for sensitive electronics.

Let me clarify this. Relocate the amp. Don't eliminate the outdoor GFCI.

Ben Miller



--
Benjamin D. Miller, PE
B. MILLER ENGINEERING
www.bmillerengineering.com

Ben Miller wrote:
"Ben Miller" wrote in message
...
The
solution is to use a non-GFCI receptacle for sensitive electronics.

Let me clarify this. Relocate the amp. Don't eliminate the outdoor GFCI.

Ben Miller



--
Benjamin D. Miller, PE
B. MILLER ENGINEERING
www.bmillerengineering.com

That was my thought too, that the injected signal from the GFCI may be
the source of the problem. But one would think that the signal would
be designed so that it would not cause problems with properly
functioning power supplies in electrical eqpt. So, it seems possible
the real problem may be with the amp.

According to :

Ben Miller wrote:
"Ben Miller" wrote in message
...
The
solution is to use a non-GFCI receptacle for sensitive electronics.

Let me clarify this. Relocate the amp. Don't eliminate the outdoor GFCI.

Ben Miller

That was my thought too, that the injected signal from the GFCI may be
the source of the problem. But one would think that the signal would
be designed so that it would not cause problems with properly
functioning power supplies in electrical eqpt. So, it seems possible
the real problem may be with the amp.

Manufacturers always try to cheap out on manufacturing costs. Removing/
reducing filtering (that most people won't notice the lack of) is one
way to reduce manufacturing costs.

Eg: "cheap" dimmers make more electrical noise than the premium ones.
This will be the same with GFCIs.

Theoretically, there are certain limits on how far they can go (eg:
FCC limits on EMI), but some manufacturers will skim as close as
they can, and other manufacturers will aim higher.

So, a GFCI from a different "line" or manufacturer _might_ help.

But I tend to agree - sounds more like an inadequately filtered amp.

A line filter from Radio Shack or such like may be the best approach.

It is _remotely_ possible that there's a grounding problem on the
outlet (which in most cases the GFCI would catch, but....). A outlet
test might be a good idea.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.

wrote in message
oups.com...
That was my thought too, that the injected signal from the GFCI may be
the source of the problem. But one would think that the signal would
be designed so that it would not cause problems with properly
functioning power supplies in electrical eqpt. So, it seems possible
the real problem may be with the amp.

I actually was a bit inaccurate in my original response. The signal is
typically full-wave pulses (120 hz) zero-referenced by a capacitor. It is
therefore a 120 hz ac signal with sharp points, which produce harmonics. The
higher frequencies will find their way into the amp more readily than the 60
hz power. A marginal amplifier design certainly could make the problem
worse, while a good design might be unaffected. There could also conceivably
be differences in the injected signal from one GFCI manufacturer to another.

Of course, I could be wrong, and one of the other responses could be
correct. The proof would seem to be in the fact that plugging it into
another outlet resolves the problem.

Ben Miller
--
Benjamin D. Miller, PE
B. MILLER ENGINEERING
www.bmillerengineering.com

On Thu, 18 May 2006 09:26:55 -0500, "Ben Miller"
wrote:

"Ben Miller" wrote in message
...
The
solution is to use a non-GFCI receptacle for sensitive electronics.

Let me clarify this. Relocate the amp. Don't eliminate the outdoor GFCI.

If the amp is outdoors, it should be on a GFCI. Get a power filter.

Ben Miller wrote:

wrote in message
oups.com...

That was my thought too, that the injected signal from the GFCI may be
the source of the problem. But one would think that the signal would
be designed so that it would not cause problems with properly
functioning power supplies in electrical eqpt. So, it seems possible
the real problem may be with the amp.

I actually was a bit inaccurate in my original response. The signal is
typically full-wave pulses (120 hz) zero-referenced by a capacitor. It is
therefore a 120 hz ac signal with sharp points, which produce harmonics. The
higher frequencies will find their way into the amp more readily than the 60
hz power. A marginal amplifier design certainly could make the problem
worse, while a good design might be unaffected. There could also conceivably
be differences in the injected signal from one GFCI manufacturer to another.

Of course, I could be wrong, and one of the other responses could be
correct. The proof would seem to be in the fact that plugging it into
another outlet resolves the problem.

Ben Miller

Once upon a time I took an old GFI receptacle apart, and if my memory
is accurate, I remember seeing NO electronics, only magnetic coupling
-- enough to trip the contacts when an off balance current existed.
On the other hand, there WAS a resistor for the test function to
puposely provide an off balance current.
Now I'm sure someone who actually knows will correct me if I'm wrong,
and I will see if I still have the taken-apart GFI at home to look at
again.
My vote on the noise would be position of the amp, maybe there is a
mercury vapor light near the outside plug, or on that same circuit, or
maybe the ground is not properly connected as someone else suggested.
--Phil
--
Phil Munro Dept of Electrical & Computer Engin
Youngstown State University
Youngstown, Ohio 44555
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"Phil Munro" wrote in message
...
Once upon a time I took an old GFI receptacle apart, and if my memory
is accurate, I remember seeing NO electronics, only magnetic coupling
-- enough to trip the contacts when an off balance current existed.
On the other hand, there WAS a resistor for the test function to
puposely provide an off balance current.
Now I'm sure someone who actually knows will correct me if I'm wrong,
and I will see if I still have the taken-apart GFI at home to look at
again.

There is significant electronics in a GFCI receptacle. Look for a circuit
board with at least one IC and a bunch of diodes, caps, and resistors. Some
have gone surface mount.

Ben Miller


--
Benjamin D. Miller, PE
B. MILLER ENGINEERING
www.bmillerengineering.com

Phil Munro wrote:
Ben Miller wrote:

wrote in message
oups.com...

That was my thought too, that the injected signal from the GFCI may be
the source of the problem. But one would think that the signal would
be designed so that it would not cause problems with properly
functioning power supplies in electrical eqpt. So, it seems possible
the real problem may be with the amp.

I actually was a bit inaccurate in my original response. The signal is
typically full-wave pulses (120 hz) zero-referenced by a capacitor. It is
therefore a 120 hz ac signal with sharp points, which produce harmonics. The
higher frequencies will find their way into the amp more readily than the 60
hz power. A marginal amplifier design certainly could make the problem
worse, while a good design might be unaffected. There could also conceivably
be differences in the injected signal from one GFCI manufacturer to another.

Of course, I could be wrong, and one of the other responses could be
correct. The proof would seem to be in the fact that plugging it into
another outlet resolves the problem.

Ben Miller

Once upon a time I took an old GFI receptacle apart, and if my memory
is accurate, I remember seeing NO electronics, only magnetic coupling
-- enough to trip the contacts when an off balance current existed.
On the other hand, there WAS a resistor for the test function to
puposely provide an off balance current.
Now I'm sure someone who actually knows will correct me if I'm wrong,
and I will see if I still have the taken-apart GFI at home to look at
again.

I would think all the ones ever made would have to have electronics, as
the goal is to detect a fault of milliamps and then trip. Without
electronics I don;'t see how that is possible. Per the above
discussion, the ones I'm familiar with do inject a test current in the
downstream line. The purpose of this is to be able to detect a fault
from neutral to ground with no loads plugged in. Without a small test
current, that isn't possible.





My vote on the noise would be position of the amp, maybe there is a
mercury vapor light near the outside plug, or on that same circuit, or
maybe the ground is not properly connected as someone else suggested.
--Phil
--
Phil Munro Dept of Electrical & Computer Engin
Youngstown State University
Youngstown, Ohio 44555
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customers drift off to free webmail services install your own
web gateway!
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