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Cheap fix on Ground Loop


derrickdj1

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Good grief.....show me the statistics that support your claim of extreme danger.

Good read by a company who actually makes this stuff, explaining what exactly the risk is.

http://peavey.com/support/technotes/safety/shockhazard.cfm

If you're lazy...

"Whenever audio equipment is operated without a ground (floating chassis), strange things can happen. Under certain conditions the amplifier will be more susceptible to radio frequency interference (picking up radio stations or CB. radio). Also, without a suitable ground, amplifiers sometimes "hum" more when the musician picks up his instrument and provides a "pseudo" ground through himself. Both of these problems are, of course, very annoying. The only solution is to find a ground point to connect to the chassis, such as a water pipe. Sometimes this may just cause more problems, when what appears to be ground turns out not to be!

One of the problems with appliances and equipment which have a "floating metal case" is that a shock hazard exists if the case comes into contact with the hot wire. This so called "fault condition" may happen in many ways with some of the more common causes being a "pinched" line cord, failure of installation systems, or movement of components due to shock or vibration which will cause the "hot wire" terminal to touch the case. Naturally, if for any reason the case does become "live," then a person touching it may be shocked if he is grounded. If this "hot chassis" is connected to another chassis or instrument by a typical shielded cord, then that chassis or instrument will become hot also. The entire purpose of the present three wire system is to provide a separate ground path which will effectively eliminate any possibility of shock.

...

The following is a list of problem areas which should be avoided with suggestions to prevent a serious shock hazard:

1. Never use two wire "extension" cords.

2. Never use extension cords with non-polarized plugs or ones with broken off ground pins.

3. Never break off the ground pin on electric equipment.

4. If necessary, always use a suitable ground adapter... and if possible, ground that extra wire on the ground adapter.

5. If no ground exists... find one... but make sure it is ground.

6. Always check the integrity of a "strange" power plug with a ground monitor device... if it checks "bad" don't plug into it!!!

7. Always use a qualified electrician to do all your "wiring."

"

 

 

The adapter "solution" directly goes against the first three.  Also a humorous quote from higher up:

 

"In order to use modern equipment in these older buildings, some people simply "break off" the ground prong from the plug. Although "ground adapters" are readily available, a few users simply "can't be bothered.""

 

 

This is actually worse, you have a perfectly good ground just sitting there and you're purposely bypassing it, not just being lazy.  

Edited by MetropolisLakeOutfitters
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If you're lazy... "Whenever audio equipment is operated without a ground (floating chassis), strange things can happen. Under certain conditions the amplifier will be more susceptible to radio frequency interference (picking up radio stations or CB. radio). Also, without a suitable ground, amplifiers sometimes "hum" more when the musician picks up his instrument and provides a "pseudo" ground through himself. Both of these problems are, of course, very annoying. The only solution is to find a ground point to connect to the chassis, such as a water pipe. Sometimes this may just cause more problems, when what appears to be ground turns out not to be! One of the problems with appliances and equipment which have a "floating metal case" is that a shock hazard exists if the case comes into contact with the hot wire. This so called "fault condition" may happen in many ways with some of the more common causes being a "pinched" line cord, failure of installation systems, or movement of components due to shock or vibration which will cause the "hot wire" terminal to touch the case. Naturally, if for any reason the case does become "live," then a person touching it may be shocked if he is grounded. If this "hot chassis" is connected to another chassis or instrument by a typical shielded cord, then that chassis or instrument will become hot also. The entire purpose of the present three wire system is to provide a separate ground path which will effectively eliminate any possibility of shock. ... The following is a list of problem areas which should be avoided with suggestions to prevent a serious shock hazard: 1. Never use two wire "extension" cords. 2. Never use extension cords with non-polarized plugs or ones with broken off ground pins. 3. Never break off the ground pin on electric equipment. 4. If necessary, always use a suitable ground adapter... and if possible, ground that extra wire on the ground adapter. 5. If no ground exists... find one... but make sure it is ground. 6. Always check the integrity of a "strange" power plug with a ground monitor device... if it checks "bad" don't plug into it!!! 7. Always use a qualified electrician to do all your "wiring." " The adapter "solution" directly goes against the first three. Edited by MetropolisLakeOutfitters, 10 December 2014 - 02:55 PM.

 

That is a nice summary.  The bottom line is don't use the cheater plug except to diagnosis a problem.  That is what this cheap fix is about, eliminating the annoying hum and safety.

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High end amps used to have a "Lift Switch".  What do you suppose that did?  Did it just lift the cable ground or did it lift the chassis ground

or is that the same thing?

 

In pro audio equipment, it kills the ground in XLR cables to prevent ground loops.  It's not bypassing the electrical ground for the chassis.  

 

http://www.audiomasterclass.com/ground-lift-what-is-it-what-do-you-do-with-it-what-do-you-do-if-you-haven-t-got-it#.VIi5LzHF9W0

 

"Where equipment requires an earth, it is vital to life not to disconnect it."

Edited by MetropolisLakeOutfitters
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Craig, I remember the days before three prong.  Been whacked many times by 110 loose on an amp...or whatever.  First time I got shocked was when I was about 6.  My dad was trying to find the bad bulb in a Christmas tree string.  He went to do something, and I picked up the string in stuck my finger in the socket. Pretty sure it was Jesus in person who pulled my finger out of it.  

 

Experiential learning.  Awesome if you survive...

 

Dave

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If a good ground/neutral does not exist in your circuit you can simply make one by hammering a ground rod into the earth and wire the ground up to your circuit(s), i have seen cold water lines and conduit used also but normally it will not be to code but most places have their own rules for this so be sure to follow them.

Edited by jason str
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Actually should mention this one.  Had a house in northern Thailand that was 240/50Hz.  The wires to the lights were stapled to the wall.  There was a wall sconce that kept flickering.  I got up on a ladder to see what the deal was and steadied myself by putting my hand on the wall...contacting a staple that was through the wire and live.

 

Found myself in the middle of the room looking up and thinking (Seriously!) "Wow...there's at least a third of an octave difference between a 60Hz shock and a 50Hz shock!"

 

Dave

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First time I got shocked was when I was about 6.  My dad was trying to find the bad bulb in a Christmas tree string.  He went to do something, and I picked up the string in stuck my finger in the socket. Pretty sure it was Jesus in person who pulled my finger out of it.  

 

Experiential learning.  Awesome if you survive...

 

My dad was a master electrician for over 20 years in an industrial environment, was usually careful but he second guessed something once and got bit by 480 volts.  

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Actually should mention this one.  Had a house in northern Thailand that was 240/50Hz.  The wires to the lights were stapled to the wall.  There was a wall sconce that kept flickering.  I got up on a ladder to see what the deal was and steadied myself by putting my hand on the wall...contacting a staple that was through the wire and live.

 

Found myself in the middle of the room looking up and thinking (Seriously!) "Wow...there's at least a third of an octave difference between a 60Hz shock and a 50Hz shock!"

 

Dave

 

Probably not a bad idea to run on the outside of the stud cavity although stuff like that will not pass code around these parts, what scares me is working on older homes where bare wire is hidden behind the walls and its kinda hit and miss when remodeling.

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what scares me is working on older homes where bare wire is hidden behind the walls and its kinda hit and miss when remodeling.

My ex's grandfather's house she was living in just halfway burned down because of this, some kind of old bare wire in the attic caught it on fire.

As for walls, even cheap stud finders do a pretty good job of telling you where the wires are. I'd be scared about a detector screwing up whether or not the wires were bare. Drill bits or a properly placed nail can make romex bare enough in a split second.

Edited by MetropolisLakeOutfitters
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what scares me is working on older homes where bare wire is hidden behind the walls and its kinda hit and miss when remodeling.

My ex's grandfather's house she was living in just halfway burned down because of this, some kind of old bare wire in the attic caught it on fire.

As for walls, even cheap stud finders do a pretty good job of telling you where the wires are. I'd be scared about a detector screwing up whether or not the wires were bare. Drill bits or a properly placed nail can make romex bare enough in a split second.

 

 

Sorry to hear about the fire, hope everybody made it out of the house.

 

The problem is older homes use plaster witch has a wire mesh over wood lath, stud finders do not work great through so many layers of material.

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My dad was a master electrician for over 20 years in an industrial environment, was usually careful but he second guessed something once and got bit by 480 volts.

 

I once took a course in basic electronics taught by an Aggie triple E.  I asked him how guys like him made it to retirement.  He said "Always keep one hand in your pocket."  I've been hit many times since then, but I pretty much obeyed that rule so I've never completed a circuit across my chest.  That's the one that will kill you most certainly.

 

Dave

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I once took a course in basic electronics taught by an Aggie triple E.  I asked him how guys like him made it to retirement.  He said "Always keep one hand in your pocket."  I've been hit many times since then, but I pretty much obeyed that rule so I've never completed a circuit across my chest.  That's the one that will kill you most certainly.

My degree is in telecomm but that basically means I got a bachelors in electrical engineering then transferred all my classes to a new program so I could be the first graduate. Sad thing is, even with an EE degree, I can't wire a house to save my life, AC is magical to me. Low voltage DC, no problem. Make me do something with AC though and I get real stupid. I did wire up my theater room, kitchen, and living room but it took forever and I had lots of consulting. :) I know some of the theory but can't picture in my head how AC works.

Edited by MetropolisLakeOutfitters
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High end amps used to have a "Lift Switch".  What do you suppose that did?  Did it just lift the cable ground or did it lift the chassis ground

or is that the same thing?

 

In pro audio equipment, it kills the ground in XLR cables to prevent ground loops.  It's not bypassing the electrical ground for the chassis.  

 

http://www.audiomasterclass.com/ground-lift-what-is-it-what-do-you-do-with-it-what-do-you-do-if-you-haven-t-got-it#.VIi5LzHF9W0

 

"Where equipment requires an earth, it is vital to life not to disconnect it."

 

I just picked up some of these... http://www.amazon.com/gp/product/B00FC4YPL4/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

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Since I added the bass shakers and another amp in the system I have had a ground loop hum.  Sometime the humming is noticeable and at other times not to noticeable.  Someone in another thread said he found a cheap fix that got rid of most of his hum.  I had a hum another time and people recommend , I think autoformer which cost a bit.  Today I got this device for around $ 6 from ebay and so far it is wonderful.  The hum is completely gone.  It did take about 30 seconds to install.  This was cheaper an easier than changing cable, outlets and the tedious job of trying to eliminate  the hum.

 

http://www.ebay.com/itm/RCA-NOISE-AUDIO-FILTER-GROUND-LOOP-ISOLATOR-HUM-KILLER-/400231421249?pt=US_Car_Audio_Video_Interconnect_C

I'm sorry and this is only my HO but you cannot get a pair (or 1 for that matter) of high quality (good freq response down to 20Hz and at low distortion levels) audio transformers for 6 bucks.

Edited by babadono
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Don,

Are you bit of an alarmist? In an audio/video system the inter-connecting cables pass ground from one device to the next....as long as one device has an earth ground they all have earth ground...the added 3 wires power cable is what completes the loop! The only way a piece of gear could become a danger is if the inter connecting cables either went up in smoke or were disconnected. Yup using cheater plugs does lower the safety margin a minute amount but geezzzz it's not as big of a deal as you're making out to be...

 

It really is a big deal - that is, if you value your life or the lives of your family. Grounding through interconnects is definitely not a good idea. I'm going to say it again: use cheater plugs only as a diagnostic aid, then remove them and fix the problem properly.

 

 

 

Josh my "personal" preferred method is no earth ground at all...I use GFI protection which IMHO is about as safe as safe can be.

 

This is a good, safe method. The NEC preferred method for GFCI connection is 2 wire ungrounded. However, the fact that a ground loop occurs is evidence that conventional 3 wire safety ground type circuits are in use.

 

 

 

 Good grief.....show me the statistics that support your claim of extreme danger............

 

There are 30,000 non-fatal shock accidents per year, with 60 fatal electrocutions per year in the US, 2008 data. This is with safety grounding.

 

for instance back in the day that high voltage tube electronics ruled the day not a single device came equipped with a 3 wire grounded power cord.... show me the statistics to support large numbers of death by electrocution from such devices.

 

Safety grounding has absolutely nothing to do with the secondary of the transformer, just the line side of the transformer. I'm sorry I do not have 50 year old data on electrocutions, but I witnessed a guitar player in 1972 who was badly shocked when he grabbed a mic stand with one hand while holding the neck of his electric guitar with the other. He was taken to the hospital and survived, thankfully.

 

   Again I'm not arguing the fact that a grounded power cord adds a very small degree of safety....but to state that running without a ground is a sure fire way to death is just silly! The truth is the chances of harm are about a million to one....

 

Let me ask you something. Why has the NEC and Underwriters Labs mandated 3 wire safety grounding or GFCIs on 2 wire circuits if it's no big deal? I never said "it was a sure way to death", but it is standard practice and will prevent someone from getting injured or killed. It's there in case something goes wrong. Suggesting that "it's silly" and a "small degree of safety" is foolish and irresponsible when posting in a forum where newbies are seeking expert advice.

 

Edited by Don Richard
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Has nothing to do with typical safety, but watch the behind the scenes footage of metallicas through the never sometime. Basically they fire up a giant tesla coil above the stage. There are actually three different guys with kill switches in case somebody walks into the kill zone and gets shocked. Every now and then a stray lightning bolt comes down and shocks the instruments while the tech is tuning them. Fascinating.

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Remember, Neutral and Ground (White/Green) both go to the same spot in your circuit panel (bonded together as stated earlier), which is coupled to an earth ground. If the item uses a 3 prong plug, it has two paths to chose from to go to your earth ground at your box. When you have multiple paths, you create the potential for a ground loop.

 

Your AVR, Amp, Bluray, etc, etc are your multiple circuits.

 

You can't assume all grounds have the same potential either. Different lengths/gauges of wire will have different resistive values.

 

Here is a snipit from Episode 134 of Ham Nation where Bob Heil takes a moment to explain ground loops.

 

You don't want to UNGROUND your system! You just want to setup one path to ground.

 

https://www.youtube.com/watch?v=oUJLE7sKbp0

 

Who is Bob Heil: http://en.wikipedia.org/wiki/Bob_Heil

Edited by Beechnut
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High end amps used to have a "Lift Switch".  What do you suppose that did?  Did it just lift the cable ground or did it lift the chassis ground

or is that the same thing?

 

Yup.

 

A lift switch does the same thing as a 3 prong to 2 prong plug. Creates a single path to ground using the neutral wire.

Edited by Beechnut
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I'm sorry and this is only my HO but you cannot get a pair (or 1 for that matter) of high quality (good freq response down to 20Hz and at low distortion levels) audio transformers for 6 bucks.

 

Give a day or two and I will post some distortion graphs of the sub.

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