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Old 20th June 2013, 05:07 PM   #1
roosar is offline roosar  United States
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Default Headphone Amp Feels 'Electrified'

Hello all,

I've been searching on Google and I can't find any answers to my questions, but I probably don't really know how to ask properly.

My problem is my headphone amp, which is a simple mint tin cmoy feels 'electrified' when I touch it sometimes. It only seems to be a problem from certain sources (like my SACD player). I have checked many different RCA to 3.5mm cables to make sure there isn't simply a short in the cable.

The amp still sounds good when I use it, but it is making me nervous that it feels like this to touch. I don't want to get shocked...

So my questions are:

1. Is it safe to use in this state?

2. Should I be trying to prevent this and how should I do it?


Thanks very much!

Robert
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Old 20th June 2013, 05:25 PM   #2
maxw is offline maxw  United Kingdom
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Is it powered by batteries? Can you measure the part you are feeling with a multimeter?
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Old 20th June 2013, 05:45 PM   #3
Mooly is offline Mooly  United Kingdom
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I think I know the effect you mean. I've felt this on (perfectly safe and grounded) appliances in the home over the years. You can feel it in your fingertips as you run them over the surface.

Also, any equipment that runs with an SMPS can inductively/capacitively couple from the high voltage side to the low. You see (and feel for real) that on TV's etc when connecting for example the aerial lead.
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Old 20th June 2013, 05:47 PM   #4
jcx is offline jcx  United States
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likely chassis leakage current - up to 1 mA is allowed in consumer equipment - gives definite sensation on touch

the current to safety gnd could be verified with a multimeter

lots of lower power consumer electronics today is double insulated/floating - two wire mains plug - but some of the mains AC still couples across the transformer pri-sec parasitic capacitance


safety codes aren't logical - you should be able to attach a safety gnd to any metal case of a double insulated floating device - but it may not be allowed


depending on which piece of your equipment is most responsible for the leakage current, some of the current may flow in your cable shield - more copper in the shield helps prevent hum in that situation
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Old 20th June 2013, 05:59 PM   #5
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Probably not grounded properly, some CD players use 2 cables for AC with no erth, these devices are regarded as electrically safe, although higher end gear tends to be grounded.

I think it would be a medical miracle if a cmoy harmed someone by electric shock in normal use.

There will be threads about cmoy grounding so you could look at that and check your build.
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Old 20th June 2013, 08:12 PM   #6
roosar is offline roosar  United States
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Default Thanks

Thanks for all of the quick replies. It does run on batteries or a linear regulated PSU (I've tried both) and I have felt the 'electrified case' when it has been attached to my SACD player (which does only have two prongs for the AC mains) and my Xbox 360 which also only has two prongs even though it still uses a Mickey Mouse plug from the PSU to the wall. I'll try to experiment with some different devices (like my blu-ray player, ps3, etc.) and some different plugs throughout the house...now that I think about it, I remember some of my downstairs outlets did register a ground fault when I tested them upon moving into my house. I'll try one of my good outlets upstairs.

Thanks again,

Robert
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Old 21st June 2013, 03:40 PM   #7
roosar is offline roosar  United States
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Hi again everyone,

I did test the outlet the SACD player was attached to, and there was an open ground. I switched to a proper outlet and I am still having the problem, so I guess it is probably leakage current. Sounds like it still safe to use though and I haven't noticed any difference in the sound.

Thanks,

Robert
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Old 21st June 2013, 04:58 PM   #8
Mooly is offline Mooly  United Kingdom
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Robert, I notice you now think you have a real ground fault in your domestic wiring. That's the point where you must for your and everyone else's safety, get it professionally checked/tested and fixed. If there is a fault then you can't take chances. Mains wiring doesn't give second chances.
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Old 21st June 2013, 05:50 PM   #9
roosar is offline roosar  United States
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Thanks for the heads up. I have a friend who is a contractor, so I'll give him a call and see if he can help me investigate further. I appreciate it...


Robert
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Old 21st June 2013, 05:54 PM   #10
Mooly is offline Mooly  United Kingdom
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No problem Hope that you get it sorted.
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