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Author Topic: brain storm an optimal human safety system for back line  (Read 95569 times)

Stephen Swaffer

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Re: brain storm an optimal human safety system for back line
« Reply #160 on: February 10, 2015, 01:34:08 pm »


The picture I posted above is different, its a the 110 volt version I what I used with my rig. It would detect missing neutral, reverse polarity, no earth, and no power etc. Logically integrating these functions with an RCD will get you close for not many $$$

As Mike often points out this tester ASSUMES a correctly connected ground for polarity detection.  And the RPBG will show as a correctly wired receptacle-but still energize the chassis of any 3 wire plug and cord connected gear.  That is the dangerous-and most difficult to detect-condition JR is trying to prevent.





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Steve Swaffer

John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #161 on: February 10, 2015, 01:48:17 pm »

As Mike often points out this tester ASSUMES a correctly connected ground for polarity detection.  And the RPBG will show as a correctly wired receptacle-but still energize the chassis of any 3 wire plug and cord connected gear.  That is the dangerous-and most difficult to detect-condition JR is trying to prevent.

I think the picture does not agree with the story... Peter has written that the tester grabs a reference from a human touching it. That indeed sounds like a NCVT and I suspect a simple NCVT could be made from neon lamps (I plan to order some and confirm that for myself).

That picture OTOH looks like one of the sundry crude outlet testers that ASSumes ground is 0V so can be tricked by bootleg wiring. In light of the number of reversed polarity outlets I've found in my house, I am very glad they didn't try to wire up grounded outlets by grabbing neutral.   :o :o

Maybe Peter can share a picture of the tester he is talking about, with the human reference contact. 

JR
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Jonathan Johnson

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Re: brain storm an optimal human safety system for back line
« Reply #162 on: February 10, 2015, 02:49:11 pm »

OK, have it buttoned up... wimpy ground wire and not a 300v Y cap but it's good enough for testing the concept.

3 pos switch so one way is hard ground, middle is ground lifted, and other side is 0.047 uF stinger cap.

<picture of an inline GFI with a toggle switch poking out of it>

Sorry, not going to work. It doesn't look like it's going to improve the sound. I know you don't want to color the sound, but in order to get accepted by the guitarist market, it at least has to look like it is going to "enhance" the sound in some way. A guitarist may not want to plug in anything that affects their sound, but they won't see the value in anything that doesn't.

Think audiophool (which I'm convinced many guitarists are, at heart, but without the cash to back it up). And looking like a plastic blob with a wart (toggle switch) poking out of it isn't going to win any awards in the "it looks like it'll sound great" department.

Maybe if you encase it in black marble and charge at least four figures.
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #163 on: February 10, 2015, 03:43:07 pm »

Sorry, not going to work. It doesn't look like it's going to improve the sound. I know you don't want to color the sound, but in order to get accepted by the guitarist market, it at least has to look like it is going to "enhance" the sound in some way. A guitarist may not want to plug in anything that affects their sound, but they won't see the value in anything that doesn't.
Never say never...  I just shipped it off to an old friend to do some real world testing.  I plugged a neighbor kids small peavey amp into it and I couldn't hear a difference in any of the three positions (as it should be). The guitar amp should be quiet wrt itself.

The friend of mine suggested that this might help with ground loops(?) While I am not sure what kind of ground loops you encounter at the front end of a guitar amp... Or maybe I should say I don't really want to know... If there are other grounds attached, that suggests that my cap ground lift is not really protective, but I'll deal with that when I learn more about his application

He mentioned input ground noise in connection with a high gain amp he is designing (same guy who designed the 5150 for Eddie Van Halen) so when he says high gain I believe him.  8)
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Think audiophool (which I'm convinced many guitarists are, at heart, but without the cash to back it up). And looking like a plastic blob with a wart (toggle switch) poking out of it isn't going to win any awards in the "it looks like it'll sound great" department.
If I was serious about merchandising a premium versions of this I'd push the human safety angle for big name talent, or sound providers with a conscience. But I don't want to pay for some tort lawyers kid's college expenses so don't plan to sell these myself.  A simple Y cap, or perhaps a 7mA fuse ground mod to a commercial GFCI seems simple enough for DIY.
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Maybe if you encase it in black marble and charge at least four figures.

I never had the stomach to deal in snake lubricant. I was a value guy before there was such a thing. 

JR
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Jonathan Johnson

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Re: brain storm an optimal human safety system for back line
« Reply #164 on: February 10, 2015, 03:48:02 pm »

Maybe if you encase it in black marble and charge at least four figures.

In case you didn't figure it out, that entire post was intended to be sarcastic.  ;)
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #165 on: February 10, 2015, 04:17:00 pm »

In case you didn't figure it out, that entire post was intended to be sarcastic.  ;)

You may be kidding but the tone-sound quality thing is as serious as a heart attack. Musicians will play though dangerous legacy amps in pursuit of some elusive tone.

I trust my friend's ears to identify if there is any sound quality issue (he's an actual design engineer who designed guitar amps and now makes pedals). I was just going for "as good as" but he suggested it might actually be better.

We'll see. I'll be happy with "as good as".

JR
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Peter Morris

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Re: brain storm an optimal human safety system for back line
« Reply #166 on: February 10, 2015, 06:17:35 pm »

I think the picture does not agree with the story... Peter has written that the tester grabs a reference from a human touching it. That indeed sounds like a NCVT and I suspect a simple NCVT could be made from neon lamps (I plan to order some and confirm that for myself).

That picture OTOH looks like one of the sundry crude outlet testers that ASSumes ground is 0V so can be tricked by bootleg wiring. In light of the number of reversed polarity outlets I've found in my house, I am very glad they didn't try to wire up grounded outlets by grabbing neutral.   :o :o

Maybe Peter can share a picture of the tester he is talking about, with the human reference contact. 

JR


The neon tester I mentioned was something I built as an apprentice. I think it was probably exactly what you have in mind.

FWIW although I have a lot of experience with electrical systems I have not in general participated in this thread because the electrical systems you have in the US are quite different from my experience.

We don’t have this problem. I have never seen or encountered a boot leg earth – never! We also don’t have bustard legs or whatever you call them where you centre tap one of your 3 phase delta windings and connect it to earth – 120V + 208V + 240 etc.

Everything is 3 phase star/delta. The earth is bonded to the neutral throughout the entire electricity distribution system and at every main switch board. RCD’s (GFCI) have been required for many years to be installed at the switch board so that the wiring throughout the building is also protected. 

…. anyway, I chose my words carefully, with respect to the power-point tester + GFCI comment and said “almost”  and “get you close”, i.e. not quite everything you need ;) ..still working on that  :-\
 
« Last Edit: February 10, 2015, 06:22:57 pm by Peter Morris »
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Stephen Swaffer

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Re: brain storm an optimal human safety system for back line
« Reply #167 on: February 10, 2015, 07:01:25 pm »

My post was mainly meant for casual readers of this thread-seeing that picture followed by "detects reverse polarity" when dealing RPBG grounds could be hazardous.  These testers have their place-in a situation where multiple pieces of gear will be interconnected while being powered from different receptacles they are not really up to the task.

Neutral is bonded to earth here as well.  In your systems, do you have a neutral/earth and hot at each receptacle?  While we have various systems that can be confusing, bootleg grounding and reversed polarity are mainly the result of sloppy careless work or indifference.  Unfortunately, that indifference can be deadly. 
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Steve Swaffer

Peter Morris

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Re: brain storm an optimal human safety system for back line
« Reply #168 on: February 10, 2015, 09:41:46 pm »

My post was mainly meant for casual readers of this thread-seeing that picture followed by "detects reverse polarity" when dealing RPBG grounds could be hazardous.  These testers have their place-in a situation where multiple pieces of gear will be interconnected while being powered from different receptacles they are not really up to the task.

Neutral is bonded to earth here as well.  In your systems, do you have a neutral/earth and hot at each receptacle?  While we have various systems that can be confusing, bootleg grounding and reversed polarity are mainly the result of sloppy careless work or indifference.  Unfortunately, that indifference can be deadly.

In Australia we always have an active, neutral and earth at all receptacles (GPO’s) including light fittings. In the passed an earth was not required for all light fittings. 

The issues for us in OZ, other than the condition of the wiring includes; no RCD protection, a reversed active & earth, or a poor neutral connection at the switch board or infrastructure level.  While I have never seen a boot-leg earth I believe very occasionally it does happen.

In addition all electrical work must be done by a licenced electrician and they are required by law to issue a certificate of electrical compliance for the work they do.

« Last Edit: February 11, 2015, 08:18:12 am by Peter Morris »
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Lyle Williams

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Re: brain storm an optimal human safety system for back line
« Reply #169 on: February 11, 2015, 12:37:19 pm »

If everything is from three phase and derived from the same generation source can you detect an inverted active neutral by phase?  Eg correctly wired will all be at 0deg, 120deg, 240deg while inverted wiring will be at another phase angle.

Doesn't help if they are all wired inverted.
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