Skip to main content ↑ ↓

Notice

Please note that most of the software linked on this forum is likely to be safe to use. If you are unsure, feel free to ask in the relevant topics, or send a private message to an administrator or moderator. To help curb the problems of false positives, or in the event that you do find actual malware, you can contribute through the article linked here.
Topic: Question on low level 'shock' from integrated amp (Read 8424 times) previous topic - next topic
0 Members and 1 Guest are viewing this topic.

Question on low level 'shock' from integrated amp

I just got a new integrated amp after the old one conked out after 15 years and encountered this strange phenomenon, wondering if the folks here with some experience in amp construction could help out.

When the set is plugged into the wall (3 pin grounded outlet, standard 3 pin power cord from original manufacturer), and the set is powered on, touching the front of the amp (the metal faceplate) gives a slight 'tingling' sensation on the fingers. This occurs only on the metal front piece and not on the steel metal chassis of the amp. As I probably do not have the right tools, I used a test pen to lightly touch the affected area of the amp but it didn't register anything.

The effect is intermittent, it cannot be felt when the amp is in standby mode and when powered on, the effect is only present at times. For info, the amp has a double insulation mark, and the relevant country safety marks . It was bought from an authorised distribution as well brand new.

I noticed this effect as when when my old iPod Mini (the one with the aluminium casing) is placed into a speaker cum charging station. There is a very slight (but discernible) tingling sensation when the device is powered from the charging station.

Is this some sort of current leak, or as what some folk have told me, some form of static discharged? Any opinions and assistance would be greatly appreciated, thanks!

Question on low level 'shock' from integrated amp

Reply #1 –
Your power outlet might be fake 3-pin, with earth ground connected to neutral. That's common in old houses.

Question on low level 'shock' from integrated amp

Reply #2 –
Quote from: googlebot on
Your power outlet might be fake 3-pin, with earth ground connected to neutral. That's common in old houses.


Thanks for the suggestion. I figured that is possible, but I tried it out at the shop I got it from as well and it exhibits the same issue. (Though they may also be using a fake 3-pin).

I guess the most important question is, is this safe for everyday use? I googled a bit online and seems that there are some similar questions raised by other folk for various electronic devices (E.g. laptops, mp3 players etc) but no definite answer.

Question on low level 'shock' from integrated amp

Reply #3 –
Good thinking googlebot!  You can get a little gizmo like this to test your AC outlet.  (Most hardware & home improvement stores should have them.)

The thing is, simply removing the ground should not cause you to get shocked.  The only way you should get shocked is if there is a defect that puts voltage on the chassis and a missing ground which fails to "ground out" the voltage.    (Since you're only getting a tingle and not really a shock, I won't pronounce your amp "defective".)

Quote
I used a test pen to lightly touch the affected area of the amp but it didn't register anything.
  Is that one of those things with a neon light?  If so, I think that should be a good test if you have a good ground.  But if googlebot is right and don't have a good ground reference for the test pen, the test pen won't work!

I'd be a little concerned... I'll tell you a story...    When I was in high school, my mother was cooking waffles in the kitchen and she told me that she was getting a tingle from the waffle iron.  I touched it and I didn't feel anything.  I thought it was just her imagination.  But I was wearing sneakers, and I knew about voltage, resistance, & current,  so just to make sure I put one hand on the waffle iron and reached-over and touched the water faucet...  "Bzzzzzt"  I felt the AC curent flow through my chest!    I was OK, but my first thought was, "Boy, THAT was stupid!"  I suggested that she get a new waffle iron...

Quote
This occurs only on the metal front piece and not on the steel metal chassis of the amp.
That's probably a good sign.  The chassis (and AC outlet) is probably properly grounded, and you might just be getting a little leakage from an internally generated voltage for a backlight or something.    But, it might also be a bad design or a defect, because the front panel should probably be grounded to the chassis.

Question on low level 'shock' from integrated amp

Reply #4 –
If your outlet is "fake 3 pin" with the ground hooked to neutral, then you can get a few volts on the neutral (and thus your equipment).  How much depends on how much power is being used on that circuit (all outlets on the same fuze) which would explain the intermittent nature.

You can try a ground fault interrupt adapter that will trip if significant current (5 milliamps) leaks out through either you or the ground pin.

Question on low level 'shock' from integrated amp

Reply #5 –
I'd be worried about ground currents in cables, and safety in general.
-----
J. D. (jj) Johnston

Question on low level 'shock' from integrated amp

Reply #6 –
Many electronic devices use only two pins by design. For example, my Macbook Pro's power adapter comes with two plugs, 2 and 3 pin. With the 2 pin plug its metal casing has the same "electric touch", you have described, but not with the 3 pin plug. That's usually nothing to worry about, though not the safest way possible. If the live conductor gets shorted with neutral (connected to the casing) the fuse will interrupt the circuit within milliseconds - once the current flow hits the maximum allowed (usually 16A in Europe). You would probably smell some ozone, but very probably survive . The advantage of 3 pin is that ground fault interrupters (GFI) can be used. They monitor the amount of current flowing in and out and as soon as there is only the slightest difference they interrupt the flow: perfect safety.

Question on low level 'shock' from integrated amp

Reply #7 –
Quote
You can try a ground fault interrupt adapter that will trip if significant current (5 milliamps) leaks out through either you or the ground pin.
  Another excellent sugestion!!!!    Those things used to be expensive, but you should be able to pick-up a GFI outlet at the hardware store for around $10.

Anyone who can wire-up a pair of speakers should be able to replace their existing outlet with a GFI outlet, after turning-off the power.    (If you've never done electrical wiring, it wouldn't hurt to look-up some instructions on the Net...  If you're lucky there are only 3 wires, but there are often additional wires that go to other outlets, lights, light switches, etc.)

The GFI does need a ground wire, so it won't work in an "old house" where there's no ground going into the electrical outlet-box.

Question on low level 'shock' from integrated amp

Reply #8 –
Quote from: DVDdoug on
Anyone who can wire-up a pair of speakers should be able to replace their existing outlet with a GFI outlet, after turning-off the power.    (If you've never done electrical wiring, it wouldn't hurt to look-up some instructions on the Net...  If you're lucky there are only 3 wires, but there are often additional wires that go to other outlets, lights, light switches, etc.)

The GFI does need a ground wire, so it won't work in an "old house" where there's no ground going into the electrical outlet-box.


You can get external GFCI's that look something like a power strip.  No need to dig into the house wiring if you don't want to.

They do NOT require a ground wire to work.  They trip based only on the difference between the hot and neutral wire currents.

I haven't checked code recently, but 20 odd years ago GFCI outlets were the approved way to install 3 hole outlets in a house without ground wires.

Question on low level 'shock' from integrated amp

Reply #9 –
Quote from: googlebot on
. If the live conductor gets shorted with neutral (connected to the casing) the fuse will interrupt the circuit within milliseconds - once the current flow hits the maximum allowed (usually 16A in Europe). You would probably smell some ozone, but very probably survive . The advantage of 3 pin is that ground fault interrupters (GFI) can be used. They monitor the amount of current flowing in and out and as soon as there is only the slightest difference they interrupt the flow: perfect safety.


I just want to chime in here and state that relying on your fuse / circuit breaker for personal protection in any way, shape, or form is bad bad bad.  Fuses / circuit breakers are there to protect the household wiring from long term overload (and subsequent fires).  One would be dead well before a circuit breaker would trip or a fuse would blow.

Mind you, the instantaneous (100 ms) trip speed for a EN 60898-1 circuit breaker is at current 3 to 20 times the rating.  So a 16 amp breaker won't trip "quickly" unless 48 or more amps are passing through it. 

Quote from: DonP link=msg=0 date=
You can get external GFCI's that look something like a power strip. No need to dig into the house wiring if you don't want to.

They do NOT require a ground wire to work. They trip based only on the difference between the hot and neutral wire currents.

I haven't checked code recently, but 20 odd years ago GFCI outlets were the approved way to install 3 hole outlets in a house without ground wires.

That is correct.  Current code (US) (NEC 2008 Sec. 210-7(d)(3)) only requires that they be labeled "No Equipment Ground" if they are ungrounded.  They work w/o the use of an independent ground, true regardless of regulatory differences.
Creature of habit.

Question on low level 'shock' from integrated amp

Reply #10 –
Quote from: Soap on
I just want to chime in here and state that relying on your fuse / circuit breaker for personal protection in any way, shape, or form is bad bad bad.  Fuses / circuit breakers are there to protect the household wiring from long term overload (and subsequent fires).  One would be dead well before a circuit breaker would trip or a fuse would blow.


Yes, if there is no short circuit and you happen to come between the conductors a fuse won't care until 16 A flow directly through your body (equivalent to over 3500W). In the meantime your heart will try to circulate the cooling fluid (blood) at 50/60 beats per second and probably collapse... 

Thanks for adding that. A somewhat careless post from my side...

I have a friend, who once had 220 Volts on the strings of his bass, because some jerk thought that he was a great sound effect technician. He was like frozen, couldn't move, let alone take away his hands from the strings. Another player suddenly realized what was happening and did the best he could think of spontaneously and kicked the bass out of his hands. My friend was a little confused for a couple of days and tired. Thank god that was all.

Question on low level 'shock' from integrated amp

Reply #11 –
Quote from: googlebot on
Yes, if there is no short circuit and you happen to come between the conductors a fuse won't care until 16 A flow directly through your body (equivalent to over 3500W). In the meantime your heart will try to circulate the cooling fluid (blood) at 50/60 beats per second and probably collapse.


Please stop with the dangerous misinformation.

A - Existence of a short circuit or not is beside the point.  Plenty of current to kill can and will be delivered before a common circuit breaker / fuse will blow.
B - You don't need to come "between" the conductors to be a path to ground.
C - This talk of "cooling fluid" is confusing, as you won't die from heat / burning.
D - As I cited, 16 amps is well below what you would likely receive and one amp is more than enough to kill if the path to ground passes through your chest.

EDIT:  Sorry I posted during your retraction edit.  The forum software doesn't warn about that. 
Creature of habit.

Question on low level 'shock' from integrated amp

Reply #12 –
Thanks for the tips and suggestions everyone, they have been more useful than what I've found on google. I'll definitely get my home outlets checked out and try looking around for the external GFCI. To share on my home electricals for info - I do know that typically for any amp that I use, when some lights are switched on or off in the house, there is a significant audio 'Pop' sound heard through the amp, and sometimes my external Audio DAC will need to be reset, not sure if that is sign of bad electrical wiring. : P

Update on the amp - I noticed a trend re the 'tingling' sensation when touching the amp. The effect is only felt sometimes when the amp is used, and usually, the effect goes away after the amp has been powered on for a few hours. Now obviously I wouldn't like to keep touching the frony plate to see if that tingling sensation is still there, is there any safe way to detect if there is any leakage from the front plate (I think the front plate hooks up to a couple of LED lamp indicators) with some tools from the hardware shop?

If there isn't then I guess I could also bring it down to the service center to have it checked out thoroughly. The support person I spoke to told me that the effect I felt is 'normal' and is probably due to static electricity when the amp is switched on due to a dry environment or carpeting. The thing is, I live in a 80-90% humidity region and I have the amp on a wooden rack on a tiled floor connected to the mains via a multiway adapter (share the power outlet with a camera dry cabinet) with a simple surge protector built in (the adapter has the local safety certification marks).

Question on low level 'shock' from integrated amp

Reply #13 –
I think that "rurouni" covered most of the common problems:
1) Missing or defective safety ground wire.
2) Mis-wired AC power wiring.
3) Cable TV or satellite dish wiring problem.

"rurouni" noted that the unit acted the same way in different buildings and the problem was only the front panel and not the chassis.
So somehow the unit is leaking to the front panel. That panel must have plastic mounting brackets. It might even be DC, it might be power line or transformer secondary AC or (this is a stretch) SMPS inter-stage AC.
Kevin Graf :: aka Speedskater

Question on low level 'shock' from integrated amp

Reply #14 –
Yep just to add if it helps, I'm using a very simple Marantz integrated amp. Most of the body is just painted steel, plastic front panel but the front plate that houses all the buttons/selectors is a metal plate and that's what is giving the v slight tingling. (Its not a zap but a v slight 'ripple' on the skin when u touch it - had this same effect before an old aluminium ipod mini when it was plugged into another mains charger in the house).

Hope I'm not being paranoid here, but I guess there should be a perfectly logical explanation to this since it does seem to occur in a number of very common everyday electrical items.

Question on low level 'shock' from integrated amp

Reply #15 –
I would try to get ahold of an inexpensive DVM (digital voltmeter) and touch one lead to the front panel and the other to a good ground. Try it first measuring AC voltage (which is more likely) and if not then try DC. This will be a very sensitive measurement for the presence of some sort of leakage current.

My guess is that you will measure an AC signal of about half of your line voltage.

Question on low level 'shock' from integrated amp

Reply #16 –
Bringing up an old topic, my electrician was by to change an old power panel and I asked him to check on the amp at the same time. He took a test pen to it on the suspected area and it didn't light up so he proclaimed it to be ok.

Is a test pen enough to gauge all of this? Ironically, I just got an iPad and its having the same 'issue' when plugged into a wall using the wall charger...

Question on low level 'shock' from integrated amp

Reply #17 –
Just to add, I found this off another forum after some other digging ard:

"When you use a power adapter with a non-earthed plug or mains socket (not just Apple but many of my "Double Insulated" IT/Infotainment systems) the equipment case will tend to float at half of the supply voltage. With 220V supply this therefore gives a case voltage of 110V. The voltage is clearly perceptible but the available current is tiny, often in the range of 10 microamps to one milliamp and is due to leakage effects through qualified components. It can give from a 'slight tickle' to a 'light-bite' with damp hands, and has the interesting effect of a feeling of bouncy vibrations when the back of the hand is lightly stroked over the equipment case.

If there is no supply adapter fault, then the leakage situation is mostly safe, but could cause audio/video hum, possible accessory device damage and should be considered as a mild hazard."

Source: http://discussions.info.apple.com/thread.j...threadID=614377

Question on low level 'shock' from integrated amp

Reply #18 –
Quote from: rurouni on
Bringing up an old topic, my electrician was by to change an old power panel and I asked him to check on the amp at the same time. He took a test pen to it on the suspected area and it didn't light up so he proclaimed it to be ok.

Is a test pen enough to gauge all of this? Ironically, I just got an iPad and its having the same 'issue' when plugged into a wall using the wall charger...

A test pen typically has a threshold voltage of about 85-90 volts, and my prediction was that you should see about 60 volts, so this may not have been a valid test. I'm puzzled why a "electrician" wouldn't have checked it with a voltmeter.

Seeing the problem in a completely different device is suspicious, though. I'm thinking more and more that this is placebo.

 

Question on low level 'shock' from integrated amp

Reply #19 –
Really the test pen might be better than using a expensive modern DMM. Why? Because modern meters have a very high input impedance (1 to 10 Meg) that means the meter will read a leakage voltage even if almost zero current can flow.  Old style meters and testers require a small current flow to read a voltage.  This reading on new meters is called "Phantom Voltage" not to be confused with mic pre-amp "Phantom Voltage".  It disappears with the smallest load.
Kevin Graf :: aka Speedskater