GFCI creates amplifier noise?

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

Reply to
hallerb
Loading thread data ...

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

................................................................ Posted via TITANnews - Uncensored Newsgroups Access >>>> at

formatting link

Reply to
g.a.miller

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

Reply to
Ben Miller

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

Ben Miller

Reply to
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.

Reply to
trader4

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.

Reply to
Chris Lewis

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

Reply to
Ben Miller

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

Reply to
Goedjn

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

Reply to
Phil Munro

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

Reply to
Ben Miller

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.

Reply to
trader4

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.