Andy W.'s hum and buzz blog post

[michael hurd]

More than likely it was just a large static charge, but I found out later that the outlet ( and all the others in the apartment ) were faulty with the aid of a $ 9 device.

[DrWho]

One can discount every instance of cheater plug related shocks and electrocutions, but it doesn't change the fact that it is illegal to use a cheater plug (and not connect the grounding tab on it).

Seriously, why would any real electrical engineer design something that costs more when everything in this market strives for

saving every last penny? Oh wait, because safety is an ethical concern.

Go figure.

Just some videos of musicians getting shocked by improper grounds:

http://www.youtube.com/watch?v=vy20BsIujm0&mode=related&search=

Now before someone goes and cries about the differences between "home"

and "profesisonal" products - let's first see some descriptions of the

functional difference between lifting the ground on a guitar amp and

lifting the ground on a home audio amp.

[michael hurd]

"And this guy has an audio system in this lab??? The fluorescent shop lights can be very dangerous those ballasts carry a wallop."

Sure, but the 500V potential in your tube amps ( or there abouts ) is not enough to carry a whallop?

[DrWho]

Don't worry Mike, you can just use cables, connectors, and insulation that will never wear out and therefore could never potentionally charge the enclosure to a dangerous voltage.

[jacksonbart]

Shocking!

[michael hurd]

Sure is!

[Cut-Throat]

Oh god! - This mole hill has been made into a mountain.

A few points you seem to have missed.

1. Using a cheater plug with a GFCI will probably be safer than a 3 prong plug on a regular outlet.

2. Note that if the signal ground is connected to the chassis
safety ground of the connected components, then as long as the
interconnect cables are in place the safety ground of a connected
component will be used.

3. Have you done everything else in your life to protect you from accidents more serious and frequent than using a cheater plug? Such as never riding a motorcycle, tailgating, speeding? - Lost that extra 50 lbs?. [:|]

[Andy W]

2. Note that if the signal ground is connected to the chassis safety ground of the connected components, then as long as the interconnect cables are in place the safety ground of a connected component will be used.

I was going to bring that in the blog, but since you already have, I'll mention it here...

Yes, techically, the non-grounded equipment will be "grounded" by the fact that it is connected to a grounded piece of equipment through the shield of the audio cable.

However, the shield of the audio cable can not be relied upon to carry the fault current required to open the breaker, nor is it designed to do that. Some shields are braided wire and might carry enough current (depending on the termination), but many are foil (foil provides a better shield), and definitely will not. The equipment ground is designed and certified to carry the full fault current that is required to open the breaker. Power cords for audio equipment are UL/CSA/CE certified; audio cables are not. Audio power cords, unlike lamp cords, are double insulated.

As for the other list of product types, I can't comment since I don't know the particular standard that covers those type of devices, but if they are UL/CSA/ETL tested they have met the insulation requirements for the particular type of device.

Shock hazard for audio equiment is required to be fault tolerant. Meaning no single failure may present a shock hazard to the user, so the equipment is either grounded or double insulated.

In a previous life I designed controls for gas appliances. Those devices must be two-fault tolerant (meaning any two components of the control may fail and your house won't blow up... the sofware for such devices must also be certified).

Ethics certainly plays a role in the design of audio equipment, and I'm sure that many of the rules relate to past experience, but I would never say that engineers are alarmists. I'll leave that to the media []. Sometimes when we read certain requirement we wonder what the bozo did to make that a rule. (My favorite... we don't make speakers with binding post that allow the use of "dual banana plugs." The European AC plug will fit right in. What are they going to do plug the toaster into the speaker? That won't hurt anybody. I don't know but with over 6 billion people on the planet sombody will figure out somthing.)

Insulation is much better and more reliable than in the past, but it can still fail. It is also possible that a mistake was made and not caught at the factory. I can't control what you do with cheater plugs in your own home. As an engineer I have to plan for all the possibilities.

[Andy W]

1. Using a cheater plug with a GFCI will probably be safer than a 3 prong plug on a regular outlet.

3. Have you done everything else in your life to protect you from accidents more serious and frequent than using a cheater plug? Such as never riding a motorcycle, tailgating, speeding? - Lost that extra 50 lbs?. [:|]

1. No it won't. A grounded chassis will preemptively open the breaker if the chassis becomes energized. For a GFCI to operate, the current that should be flowing in the neutral is sensed to be flowing somehwhere else (you could be the "somehwere else"). And what if the sensor fails? (Ever seen a "test" button on a GFCI? It's because they can fail and will leave you unprotected... and then they claim that since they wrote in the user's manual that you should test them monthly, they are off the hook.) I had a lightning storm take out half the GCFI's in my house a few years ago.

3. Life is not safe. But why temp fate. As always, YMMV. Do you know anybody that tests their GFCI's monthly?

[Cut-Throat]

I'm using a GFCI on the breaker not the receptacle. The GFCI on the breaker does not have to be tested monthly.

Also if the GFCI catches the Ground Fault in 1/30 of a second, that is good enough for me. My statement that the GFCI was probably safer, was not just in reference to a 'hot chassis', but from other electrical hazards as well.

You have a lot of the "What if the device fails" in your explanations. Why not ask what if the ground wire comes loose inside the Receptacle? or in the power cord?, or inside the amp?. Better check all those connections also! - You seem to imply that all of the devices associated with a separate ground are rock solid, but any other device is perched on the edge of uncertainity.

[NOSValves]

I'm still waiting for the reports of mass fatalities from 3 prong to 2 prong adaptors used in home audio systems......

I would also like to see the law that deems 2 prong adaptors illegal. I think we would need to expand the prison capacity by 10X ...

I have not stated that safety margin is not lowered by using 2 prong adaptors. I have simply stated that the margin of safety difference in the case of a home audio system is very small. If a persons IC's start smoking I would expect they would be bright enough to realise the gear is unsafe and to unplug it. Folks do silly stuff all the time like messing with anything electrical while standing waste high in water for instance.

Craig

[mas]

One can discount every instance of cheater plug related shocks and electrocutions, but it doesn't change the fact that it is illegal to use a cheater plug (and not connect the grounding tab on it).









Seriously, why would any real electrical engineer design something that costs more when everything in this market strives for
saving every last penny? Oh wait, because safety is an ethical concern.
Go figure.









Just some videos of musicians getting shocked by improper grounds:

http://www.youtube.com/watch?v=vy20BsIujm0&mode=related&search=

Now before someone goes and cries about the differences between "home"
and "profesisonal" products - let's first see some descriptions of the
functional difference between lifting the ground on a guitar amp and
lifting the ground on a home audio amp.

Can we say Stone the Crows?

Just read Bill Whitlock and Neil Muncy's stuff. Its all there.

[Andy W]

There are 6 billion "what-ifs" out there, and I don't want to be responsible for one of them dying. UL/CSA/CE certification is all about the "what-ifs". And yes, engineers sit around and dream this stuff up (or use actual cases) so people don't have to worry about it. On the other hand, we not only dream up these things, we make the assumption that it will fail. Anything else would be unethical.

Also there are defenitions/tests/inspections as to what constitutes a securely and permanently fastened ground connection. And their are inspectors who randomly show up at the factory to make sure you're still making it like the sample you submitted for testing.

Perhaps we should just leave everything live and out in the open, cuz people should know better than to touch live wires right? People do take their safety for granted.

A GCFI can only limit the time that current passes through your body, not the level of current.

You seem to imply that all of the devices associated with a separate ground are rock solid, but any other device is perched on the edge of uncertainity.

That was not my intention. A grounded chassis is two failures away from a shock hazard. A double insulated chassis is two failures away from a shock hazard, so in my mind they are equal, but different ways to achieve the same result.

[Andy W]

I would also like to see the law that deems 2 prong adaptors illegal.

I know of nothing in the US. Here's one from Canada: http://www.gov.ns.ca/enla/electricalsafety/esbadapterplugs.asp

Section 4.4 -Adapters and Current Taps, clause 4.4.2 of the above standard indicates that 2-wire to 3-wire adapters are not acceptable.

Therefore these adapter plugs are not approved for use in Canada.

The cUL approval label in this case has been misapplied and the device should never have any acceptable Canadian label or mark on the device applied in the first place.

Therefore 3 prong adapter plugs are banned effectively immediately from being sold in Nova Scotia even if they bear what appears to be an acceptable approval mark or label on the device.

Consumers should realize that these adapter plugs provide no effective bonding (grounding) of an electrical device that has a 3 prong plug and may cause a fire or shock hazard in the event the electrical device is defective or fails.

Almost all 2 prong receptacles, unless recently rewired ,are not properly bonded. Connecting the tab of the adapter plug to the screw of the receptacle does not provide any safety features against shock and such an installation may damage sensitive electronic equipment where a ground connection is required.

In order to provide some safety against shock, where older 2 wire receptacles exist, it is recommended to have an electrician install a 3 prong ground fault circuit interrupter (GFCI) receptacle to replace the existing 2 prong receptacle and reuse the existing 2 wire installation.

(Italics mine.)

[Cut-Throat]

I don't think anyone is disagreeing with you Andy. From a 'UL' standpoint you are absolutely correct. It is the emphasis of the danger that is being questioned. I don't think anyone would think that listening to a piece of Audio Gear with a cheater plug on a Circuit with a GFCI Breaker would be more dangerous than driving a car on Freeway. Yet, we all hop in our cars on a daily basis and assume a 'deadly' risk.

I am much more comfortable with my cheater plug than you should be driving your car.

[michael hurd]

Thanks for the voice of reason Andy... if we have failed to make this clear, I would like to quote you.

"A GCFI can only limit the time that current passes through your body, not the level of current."

One amp will kill. It does not matter if that amp is put through your body for a quarter of a second, or ten seconds.

I have posted a few references to where use of a cheater plug resulted in DEATH.

Would you like to gamble with life safety and security? I don't. Do what you like, but hum and buzz can be fixed may ways.

As stated, an interconnect may carry some current, but is it rated to carry the full amount of current that the grounding wire is supposed to take care of in the event of a problem? In the case of a chassis isolated RCA jack ( teflon washers on both sides ), would the interconnect do anything>?

[Cut-Throat]

Hurd dude - Then never, ever ride in a car - I am talking DEATH here! - Much more common than listening to audio gear with a cheater plug. Why gamble with your life?

Don't ever set foot in a Car - They can kill you! - I am talking 50,000 Americans every year!

Why Risk it????

And don't get me started on Heart Attacks. - Are you at your ideal weight? - Leading cause of DEATH! - Don't even think about going near that Pizza and Beer tonight!

[michael hurd]

Cut-throat. It seems that you are a little upset. I answered each of your questions, probably no one else could. Does this make me the bad guy?

[Cut-Throat]

Nope! - I am not upset at all! - I am a risk taker.

In fact right now I am sitting here listing to some Jazz with a glass of wine with my Cheater Plugs installed on my amps. And I am thrilled!

I was thinking about a little hang gliding or Bungy Jumping this evening, but those things did not cheat death as much as my 2 prong Cheater Plugs do. Hey, I do this for a thrill! Some folks just don't understand this, but I like living on the edge!

[michael hurd]

"Hurd dude - Then never, ever ride in a car - I am talking DEATH here! - Much more common than listening to audio gear with a cheater plug. Why gamble with your life?"

Because you can't control what others do, a drunk driver can cross lanes and drive over you. That being said, when you defeat a safety device YOU are the one that is in control. Again, I responded to how to fix your hum problem, and you are QUITE WELCOME!

"And don't get me started on Heart Attacks. - Are you at your ideal weight? - Leading cause of DEATH! - Don't even think about going near that Pizza and Beer tonight! "

Am I at my ideal weight? Ask anyone that was in Indy this year at the Klipsch pilgrammage, they all saw me, and yes I am very close to that. As far as pizza and beer goes, I rarely eat fast foods, ( pizza is far more healthy than slugging down a double cheezyburgler with a large fries and pop ) and I hardly drink alcohol. My job requires that I am on call 24/7/365.

Any more questions? I can PM you my phone #.