Headphone Amp Feels 'Electrified'

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
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
 
Administrator
Joined 2007
Paid Member
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.
 
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
 
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.
 
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
 
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
 
Administrator
Joined 2007
Paid Member
:cop:

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.
 
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
(X)Y safety capacitors currents
 
Ground wires are often unhooked by plumbers and then not reattached or reattached improperly. Plumbing repairs can interrupt ground path even if the plumber does not touch the ground wires. My house had this problem when I bought it; a plumber had replaced an iron pipe with a copper pipe attached with plastic bushings. The plastic bushings are to prevent corrosion caused by two dissimilar metals in contact. They also interrupted the mains ground path.
 
Interesting. I'm not sure whether running mains protective earth (or even return) over plumbing is even allowed over here. Definitely not for gas pipes, that much I know.

And yes, as mentioned this phenomenon can appear when Class II (double insulated) devices are using mains filter caps from phase and neutral to circuit ground. This essentially has ground floating at half mains voltage. Depending on capacitance values, it's also good for some nasty sparks when plugging things in.
 
Interesting. I'm not sure whether running mains protective earth (or even return) over plumbing is even allowed over here.

It's NEC code here. Only licensed union personnel are allowed to work on electrical, plumbing, and gas lines. In some areas, you have to be in a union to move a chair from one room to another :eek: but that's another rant.

Of course, it is the exception that licensed workers repair most houses. It's the difference between $120/ hr and $25/ hr. Very few homeowners are willing to pay the ridiculous price for union work. As a result, union guys don't get much work and "scabs" have more work than they can handle. A lot of union guys are "scabs" on the side of course.

Definitely not for gas pipes, that much I know.

A Three Stooges episode comes to mind. :eek:

And yes, as mentioned this phenomenon can appear when Class II (double insulated) devices are using mains filter caps from phase and neutral to circuit ground. This essentially has ground floating at half mains voltage. Depending on capacitance values, it's also good for some nasty sparks when plugging things in.

That's terrible. Everything I build is three pronged and grounded. Ungrounded outlets are obsolete here, but still commonly found. The first thin I did when I bought my house was swap the ungrounded outlets for grounded ones.

My house is grounded to the plumbing (correctly now), but my shop is grounded through two 4 foot long copper stakes driven into the ground.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.