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Cheap fix on Ground Loop


derrickdj1

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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.

 

 

Babadono,

 

He's only trying to get rid of DC hum. An AC/AC transformer won't allow DC to pass between the coils. Doesn't take an expensive transformer to eliminate DC hum/noise/current. It's just how transformers work.

 

I'm not sure what the advantage of the high dollar ones are. Frequency response (like you said), durability, quality of materials, efficiency. Love to see some REW tests on it.

 

(Just using the image to show schematic of a transformer. Don't get hung up on mutual inductance and equations/formulas)

 

tracir.gif

Edited by Beechnut
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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."

 

MLO,

 

This is what a 3 prong to 2 prong connector does. It is a ground lift. That article is on point!

 

XLR is 3 wire and a ground lift makes it 2. If you have a mic plugged into the mixer, and the mixer is running 3 prong, and the XLR doesn't have a ground lift in it, it is also running 3 wire and making multiple paths to ground. (Current can go over neutral to earth OR over ground to earth, through the chasse) Throw in a ground lift on the mic, and now current doesn't have multiple paths anymore. The only way any current in the system can get to ground is through the mixers 3 prong power cord.

 

 

male_xlr.gif

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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.

I thought that was the case but wasn't sure.

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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.

 

The images of Tesla with massive bolts flying all around him still amaze me.

 

Dave

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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.

 

 

Babadono,

 

He's only trying to get rid of DC hum. An AC/AC transformer won't allow DC to pass between the coils. Doesn't take an expensive transformer to eliminate DC hum/noise/current. It's just how transformers work.

 

I'm not sure what the advantage of the high dollar ones are. Frequency response (like you said), durability, quality of materials, efficiency. Love to see some REW tests on it.

 

(Just using the image to show schematic of a transformer. Don't get hung up on mutual inductance and equations/formulas)

 

tracir.gif

 

DC hum? In my best New York accent "Whattya talkin about?"

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Derrick,

 

Do you have any 3 prong to 2 prong adapters laying around the house? That is one way I've isolated some ground loops when working with ham radio.

 

41LC74ooslL._SL1005_.jpg

that little tab with the hole in it is SUPPOSED to be connected to the screw on the outlet cover plate that is ground.

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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............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.

 

   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....

 

only silly if it didn't happen to someone in your family.

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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.

 

 

Yep again and with as much emphasis as possible to people new to our hobby:

NEVER, NEVER, NEVER defeat the safety ground as a permanent solution to any problem you are having. Period.

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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.

Sales pitch from a company profiting from the sale of such devices..

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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.

And of the 30,000 minor shocks and 60 fatal electrocutions how many were from an audio system with one component grounded and all others lifted? Show me one news report from any year as described ....

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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.

And of the 30,000 minor shocks and 60 fatal electrocutions how many were from an audio system with one component grounded and all others lifted? Show me one news report from any year as described ....

 

 

I don't know what's wrong with you - telling people to bypass safety features is nonsense. There is NO UPSIDE IN BYPASSING SAFETY SYSTEMS.

 

Clear?

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Untold number of homes across the US with nothing but groundless receptacles. How are they making it? 

 

Looked it up: NEC said that all receptacles required to have a ground approximately 1965. Think of all those homes that do not have this feature today.

Edited by JL Sargent
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Untold number of homes across the US with nothing but groundless receptacles. How are they making it? 

 

Looked it up: NEC said that all receptacles required to have a ground approximately 1965. Think of all those homes that do not have this feature today.

 

Just because older homes are wired that way doesn't mean it's OK. Those homes are violating safety codes. The wiring needs to be upgraded to modern standards, i.e. 3 wire safety grounded or 2 wire with GFCI protection. If, for instance, the electrical system was damaged in a storm it will need to be upgraded before it will pass inspection. It's a good idea to do that anyway when dealing with 50 year or older house wiring. Besides personnel protection it can save the house from burning down.

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Untold number of homes across the US with nothing but groundless receptacles. How are they making it? 

 

Looked it up: NEC said that all receptacles required to have a ground approximately 1965. Think of all those homes that do not have this feature today.

 

Just because older homes are wired that way doesn't mean it's OK. Those homes are violating safety codes. The wiring needs to be upgraded to modern standards, i.e. 3 wire safety grounded or 2 wire with GFCI protection. If, for instance, the electrical system was damaged in a storm it will need to be upgraded before it will pass inspection. It's a good idea to do that anyway when dealing with 50 year or older house wiring. Besides personnel protection it can save the house from burning down.

 

Safety IS far more important than eliminating a mild audio annoyance. I happen to like 60 Hz. hum, it adds a nice "realism" feel to the music, like a "live in the studio" recording on Roy Buchanan's first album, playing without humbuckers. LOL.

 

There are many ways to deal with the issue without endangering anything. One of the ways is to not use separates, but modern AVR's for HT and 2 channel. Short internal connections, not loose wires except for speakers. The simpler, the better.

Edited by ClaudeJ1
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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.

Good, sound, advice here.

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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....

 

All of this AC code is designed to prevent idiots from killing themselves and others under a worse case scenario since everything plugs into a wall nowadays. Isolation is the key.

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