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Topic:
Unbalanced (L & R) over Cat 5
This thread has 38 replies. Displaying posts 31 through 39.
Post 31 made on Thursday March 2, 2017 at 22:58
highfigh
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On March 2, 2017 at 13:41, Ernie Gilman said...
If there is a ground potential difference between different "ground" points, a lower resistance/impedance along the length of the ground conductor will result in lower injection of noise. I've seen a demonstration (Middle Atlantic seminar with Bob Whitlock) of cheap-ass audio cables with very low shield resistance being quiet, while a super expensive audio cable with 5 ohms resistance long the ground conductor just hummed along!

You also have an unsafe electrical system. "How did he die?" "He made the mistake of touching the ground of something plugged into Panel B while touching the ground of Panel A."

I'd think your threat to report him to the state contractor's licensing agency would get him to take care of that. And you should probably report him whether he fixes it or not.

That definitely shows there's a potential difference ( = danger) between the two grounds.

I know- I have been dealing with ground loops for 40+ years. Also, Bill Whitlock may have done a presentation for Middle Atlantic, but he's the major force behind Jensen Transformers and all of their great White Paper tech briefs that have been linked to and quoted over the years. The first time I went to one of his presentations was in the early-'80s at CES and again in '05, when I was at CEDIA. It's always a good thing to go a learn/relearn what he has to say.

The electrician was from Illinois, he never pulled a permit and didn't respond to any calls. I found out that he never pulled the permit when the local inspector stopped by to check into the permit I had pulled for some other work and he was decent enough to let the garage work be sistered to the circuit being installed for the new furnace. Since he was there, I asked him if he wanted to check out the garage and that's when he found the code violations. I acted as the helper when the new work was done since I had worked on several jobs with the electrician when I was with another integrator, but the garage was wired about a year before.

The possibility of danger depends completely on the resistance between the two points and the current and since the garage is detached, there was little chance of contacting the ground for each. I didn't measure the voltage but the lack of a bonding conductor doesn't prove a PD, it just attempts to prevent it from existing. Regardless, it's still the current that poses the risk, not the voltage and since the neutral was intact, the difference wasn't great.

I have seen expensive cables hum like a banshee and cheap crap work very well- it definitely shoots holes in the sales pitch for something that costs more than a few cars I have owned.
My mechanic told me, "I couldn't repair your brakes, so I made your horn louder."
Post 32 made on Friday March 3, 2017 at 01:25
Ernie Gilman
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On March 2, 2017 at 22:58, highfigh said...
I know- I have been dealing with ground loops for 40+ years. Also, Bill Whitlock may have done a presentation for Middle Atlantic,

That wasn't it at all -- read on
but he's the major force behind Jensen Transformers and all of their great White Paper tech briefs that have been linked to and quoted over the years. The first time I went to one of his presentations was in the early-'80s at CES and again in '05, when I was at CEDIA. It's always a good thing to go a learn/relearn what he has to say.

I LOVE solving grounding and noise problems and have had a few good conversations with Bill. In this case, Middle Atlantic put on a seminar on noise and Bill was there to add information, correct them when needed, and answer questions that the MA guys came up with.

The electrician was from Illinois, he never pulled a permit and didn't respond to any calls.

Great. People sometimes are a real piss-off!

The possibility of danger depends completely on the resistance between the two points and the current and since the garage is detached, there was little chance of contacting the ground for each.

That's an amusing comment. If I understand what you wrote before, you use a transformer to eliminate a problem caused by interconnection of the two grounds. That is, there's a point at which one can contact both grounds.

I didn't measure the voltage but the lack of a bonding conductor doesn't prove a PD, it just attempts to prevent it from existing. Regardless, it's still the current that poses the risk, not the voltage and since the neutral was intact, the difference wasn't great.

What's a PD? Potential Difference?
I have seen expensive cables hum like a banshee and cheap crap work very well- it definitely shoots holes in the sales pitch for something that costs more than a few cars I have owned.

And it's surprising that the resistance of the cables might be the issue, too.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 33 made on Friday March 3, 2017 at 06:48
highfigh
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On March 3, 2017 at 01:25, Ernie Gilman said...
That wasn't it at all -- read on
I LOVE solving grounding and noise problems and have had a few good conversations with Bill. In this case, Middle Atlantic put on a seminar on noise and Bill was there to add information, correct them when needed, and answer questions that the MA guys came up with.

Great. People sometimes are a real piss-off!

That's an amusing comment. If I understand what you wrote before, you use a transformer to eliminate a problem caused by interconnection of the two grounds. That is, there's a point at which one can contact both grounds.

What's a PD? Potential Difference?
And it's surprising that the resistance of the cables might be the issue, too.

If you have had several conversations with him, why did you call him Bob?

That electrician and his helper were both "a real piece of work". The guy whose "company" built the garage was a referral from someone I had worked for and he's the real turd- I found out later than he has a long history of going under owing money and opening under a new name. I wouldn't piss on him if he was on fire.

I never said I used a transformer on my garage and if I did, it would have been enclosed, so there's no chance of contacting both. Besides- if I have a situation like that, I measure voltage and use a test light to find out how bad the PD is (Yes, PD= Potential Difference is the way we abbreviated it when I was in school). I wouldn't touch the house side with one hand and the garage side with the other, anyway- that's a good way to wake up dead.

Last edited by highfigh on March 3, 2017 17:02.
My mechanic told me, "I couldn't repair your brakes, so I made your horn louder."
Post 34 made on Friday March 3, 2017 at 11:17
Ernie Gilman
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On March 3, 2017 at 06:48, highfigh said...
If you hav had several conversations with him, why did you call him Bob?

I was in a hurry, no excuse.

I never said I used a transformer on my garage and if I did, it would have been enclosed, so there's no chance of contacting both.

I misunderstood this, then:
On March 1, 2017 at 10:50, highfigh said...
But using a high Z output does work, as long as grounding isn't an issue, which it was when I used Cat5e for the audio from my main system to the garage system. The electrician (turd) didn't wire it to code, so the sub-panel in the garage wasn't bonded to the main panel and I had hum. From the main stereo to the basement system, it was fine as long as I disconnected the garage or used an isolation transformer.

Besides- if I have a situation like that, I measure voltage and use a test light to find out how bad the PD is (Yes, PD= Potential Difference is the way we abbreviated it when I was in school). I wouldn't touch the house side with one hand and the garage side with the other, anyway- that's a good way to wake up dead.

Yes, you'd enclose the transformer, and I can see that you'd measure ground to ground for voltage differential when you're first checking to see what's what; but there's still danger because the existence of that differential means that anyone who EVER works with that wiring cannot assume that ground here is the same as ground right next to here.

For instance, when you start work at a client's house, do you ever measure voltage from one ground to another in advance of work to see if there's a potential, pun intended, problem? I've never done that, though seeing this, it makes sense to do it!
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 35 made on Friday March 3, 2017 at 17:26
highfigh
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On March 3, 2017 at 11:17, Ernie Gilman said...
I was in a hurry, no excuse.

I misunderstood this, then:

Yes, you'd enclose the transformer, and I can see that you'd measure ground to ground for voltage differential when you're first checking to see what's what; but there's still danger because the existence of that differential means that anyone who EVER works with that wiring cannot assume that ground here is the same as ground right next to here.

For instance, when you start work at a client's house, do you ever measure voltage from one ground to another in advance of work to see if there's a potential, pun intended, problem? I've never done that, though seeing this, it makes sense to do it!

Do I measure voltage, you mean from one system to another when I need to send audio and/or video to it for the first time? Absolutely. I think I mentioned working at a stereo store and hearing a loud snapping sound from the Pioneer A30 Class A power amp when the whole rack was connected to power, but not when the Soundcraftsman power amp was gone, which was powered by a different receptacle that turned out to be on a different circuit and phase. I have seen sparks when connecting the cable box that I had and felt a decent jolt when I unplugged the coax while my arm was laying on the cover. I have seen equipment smoke as soon as it was connected to cabling from another area of the building, even though the other equipment worked as expected.

If I have installed equipment and it's working, I don't measure but if I'm coming into a system that I didn't work on, I don't assume it was installed correctly because I have seen really shoddy work in my almost 40 years of doing this.

I have been working at a house that was wired by a company which advertised themselves as the premier AV contractor and their website had many photos of interesting jobs. I did the initial walk-through with the client and saw the structured wiring enclosure, opened it and found that the network switch, cable splitter and most of the cables were just hanging and only the phone and data punchdown modules were fastened. Above this enclosure, were speaker cables and coax that were looped and wire tied to a conduit, unused. In the adjacent laundry room is a drop of bundle (2 coax, 2 Cat5e in a blue jacket) and extra Cat5e & coax, hanging down to the floor behind the door. I also saw a 12' x 16' area removed from the ceiling (wood lath & plaster) and a couple of extra small holes in the ceiling, which I assume are from their attempt to feed cabling to the equipment at the top of the pantry cabinet in the kitchen, directly above the holes. They tried to go from the bottom, I went in from the top and I think it took me less than 15 minutes to take my cables (which didn't come from the same place as theirs) and pass them into the cabinet. They missed by 8"- if they had drilled a hole in the next joist space, they would have been able to finish, but they chose to feed the cables between the TV cabinet through the wall to the hole they cut into the cabinet and abandon the others, rather than remove them. Then, they ran bundle to a few places on the 2nd floor, but I don't measure continuity on many of them. In addition, they labeled far too many cables 'Playroom'- it uses only four and I think I counted 7 or 8 with that name. I know where one bundle goes and it's being used for the modem and router, but the blue Cat5e may be cut, pinched or they may have dead-ended them in the attic, to be assigned later. One of the coax in the bundle to the wall plate at the 2nd floor desk shows continuity, but when I connect a TV to it, the TV doesn't pick up a channel. Neither of the Cat5e shows continuity. The two Cat5e to the AV cabinet in the Sun room don't work for network, either.
My mechanic told me, "I couldn't repair your brakes, so I made your horn louder."
Post 36 made on Friday March 3, 2017 at 17:28
goldenzrule
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Damn, I didn't think anyone could be more wordy than Ernie.
Post 37 made on Friday March 3, 2017 at 19:01
highfigh
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On March 3, 2017 at 17:28, goldenzrule said...
Damn, I didn't think anyone could be more wordy than Ernie.

I could have written "The cabling sucked", but that wouldn't begin to describe it.
My mechanic told me, "I couldn't repair your brakes, so I made your horn louder."
Post 38 made on Friday March 3, 2017 at 19:20
goldenzrule
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On March 3, 2017 at 19:01, highfigh said...
I could have written "The cabling sucked", but that wouldn't begin to describe it.

Oh I don't know what the hell you wrote. I didn't read any of that :-D
Post 39 made on Saturday March 4, 2017 at 00:44
Ernie Gilman
Yes, That Ernie!
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On March 3, 2017 at 19:01, highfigh said...
I could have written "The cabling sucked", but that wouldn't begin to describe it.

And that is exactly the problem I have with writing stuff that has lots of relevant details.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
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