winesmile, you make me blush. Fortunately, my girlfriend knows I'm not God and am very approachable.

Here is my take and a few questions. Please forgive me (and correct me) if I use improper terms. This is a very new subject for me and this seemed like an advance course.

The thermal management part was unexpected, familiar, and easy.

I really learned a lot from the discussion on AC magnetic and electrical fields and how they can induce hum particularly in audio. The Pin-1 problem, why not relevant to most of my work still helped with a general understanding of how and why hum can occur. I understand why but wish they would have given a list of manufactures that are known for these issues.

Most important and the biggest "ah-ha moment" for me was bootleg grounds and voltage injecting from the neutral onto the ground.

I have a few questions for Ernie or whoever would like to field them to help me attempt to further grasp what I heard today.

They seemed to suggest that audio is far more sensitive to hum from electronic or magnetic interference than video may be. Also, that most (if not all) video rolls are caused by bootleg ground issues. I dont recall a single reference to a rolling bar being caused a non-grounded cable signal. I may have missed something with these points, please clarify if I am wrong.

The discussion on grounding a rack and isolated ground seemed simple enough. It is something I need to start paying more attention to on our racks.

They lost me when they started talking about Isolation transformers and three-phase wiring. I wanted to follow but just couldnt. It seemed to only be necessary understanding for sensitive installs in churches or recording studios with mic runs. I am sure with a greater understanding of the general concepts this would mean more to me but I just couldnt follow.

I wish they would have talked more about grounding incoming cable signals and proper methods.


Question:

Audio hum (when produced by AC magnetic or Electric field) was corrected by introducing a low OHM cable (lower resistance), twisted pair cable (cancel field), or Jensen transformer. Did I get that right?

Is it correct that the majority of video roll is from bootleg ground? This problem was addressed by either locating and correcting the bootleg, lowering the resistance of the wire, or a Parallel Earth Connector. Correct?

Twisted pair cabling was suggested for audio hum but not referenced for video roll. I am assuming this has to do with video roll being much less prone to magnetic or electric field issues that twisted pair can eliminate.


(Im posting this here to keep the discussion going so I dont forget what I learned and to make sure I took in the information properly)

This brings me to a real world scenario: A bar with a dozen TVs. Half of them roll. All using video baluns. Tested with a ground lifter (I know....I know) and roll disappeared. Obviously this isnt the solution. Twisted pair that is natural to the balun but didnt help. Now I think I know why (wasnt a noise issue). The issue is probably a bootleg ground right? I can test with an amp meter. However, from what I heard today I should be able to eliminate the roll by using a low resistance cable. Does that mean that I can use the low resistance cable for just the short run from the balun to the low resistance cable have to run the length of the run? I know this doesnt fix the problem but it should be a way to eliminate the roll, correct?

Other cool things I learned:

The blue pair on CAT5 has the tightest twist and thus performs best to reduce noise.

CFL bulbs are actually WORSE for the environment because they cause electrical plants to work much harder. Its late so I forget the exact reason but it had something to due with the non-linear wave form and the heat it creates. The fix is power factor corrected CFL currently associated with dimmable CFL.

I don't think he said exactly that. Since I had investigated this issue before, I was listening carefully for what he was going to say when I heard the issue coming up. He talked about the blue pair, then he said they are all twisted at different rates to avoid crosstalk.

I brought this up about a year ago. The question was, "are all of the CAT5s done so that the same particular colors have the same amount of twist from one product to another?

After a lot of speculation, Stephen Lampert, who literally wrote the book on installation, stated that while all manufacturers make CAT cables with different amounts of twist on each pair, there is no standard as to which cables have the most, the least, the in-between amounts of twist. Each manufacturer makes them as they see fit. People who posted here found that the particular part number they always bought were always made the same, but there's not even any guarantee that one can depend upon that.

Maybe I heard wrong, but if there was one thing I was sure of from the training it was that. Im certainly not speaking of real world examples and havent done my own test but I think he said to use the blue pair.

He said he uses the blue pair. Or "just take the blue pair...." That's a recommendation to use the first pair of the color code series; he didn't say there was anything special about the blue pair.

Since CAT cables are in pairs, and the color code is blue, orange, green, brown, it's sensible to think in terms of the color code and always use the blue pair first, and I always make a point to use the solid color for hot and the white/[color] for ground. Thus it makes sense to me that he'd call for using the blue pair -- it's a way to remember the color code and always use the wire in a way that keeps its noise immunity properties.

By the way, I remember that color code as BOG Brown. What color is the stuff in a bog? It's brown. Blue, orange, green, brown.

Using wire pairs in order of their color code is, I think, why people use black and red as a pair in four-conductor speaker wire. Why that first pair is the right channel is beyond me, as I always call the first pair the left, since we live in a society where most reading is done left to right.

edit:
Re CAT cable, I was wrong. It wasn't Steve Lampen. From [Link: remotecentral.com] we have two quotes. One is from member Other:


and from Belden, in Post 46, we have


I meant that thread, not this one.

He absolutely suggested the blue pair due to its tighter twist. I'm not suggesting it is correct. But he did say that. $ 5 wager on it? I hope this is on one of the videos.

However, a wikipedia article suggests that the green pair has more twists by length.

Many thanks for taking the time to post these questions. I have summarised a reply below:

Q. Audio hum (when produced by AC magnetic or Electric field) was corrected by introducing a low OHM cable (lower resistance), twisted pair cable (cancel field), or Jensen transformer. Did I get that right?

A. Broadly speaking yes, but the solution to the problem depends on the nature of the aggressor: When considering unbalanced interfaces: if the problem is caused by excessive ground noise currents then lowering the resistance of the signal conductors reduces the corresponding noise voltage differential that is developed across the length of the cable. If the noise is magnetically induced then using a signal interface with a tighter twist rate will minimize any magnetically induced voltage. The use of an audio-isolation transformer removes the ground noise coupling mechanism from the signal interface.

Q. Is it correct that the majority of video roll is from bootleg ground? This problem was addressed by either locating and correcting the bootleg, lowering the resistance of the wire, or a Parallel Earth Connector. Correct?

A. We can’t categorically state that video roll is predominantly caused by bootleg grounds however they are without a doubt one common cause. The other common cause is simply large ground voltage differences (between remotely located interconnected source and video equipment) that is due to high equipment leakage currents and / or Ground Voltage Induction. To address video roll check for,and correct wiring errors first; as a matter of best practice always use video signal cables that have low shield resistance (remember that you can’t tell what the resistance is just by looking at the cable – you have to measure the resistance with an accurate ohmmeter). Using a Parallel Earthing Conductor (PEC) will also help.

Q. Twisted pair cabling was suggested for audio hum but not referenced for video roll. I am assuming this has to do with video roll being much less prone to magnetic or electric field issues that twisted pair can eliminate.

A. Yes,

Q. This brings me to a real world scenario: A bar with a dozen TVs. Half of them roll. All using video baluns. Tested with a ground lifter (I know....I know) and roll disappeared. Obviously this isnt the solution. Twisted pair that is natural to the balun but didnt help. Now I think I know why (wasnt a noise issue). The issue is probably a bootleg ground right? I can test with an amp meter. However, from what I heard today I should be able to eliminate the roll by using a low resistance cable. Does that mean that I can use the low resistance cable for just the short run from the balun to the low resistance cable have to run the length of the run? I know this doesnt fix the problem but it should be a way to eliminate the roll, correct?

A. To test for the bootleg ground clamp your ammeter around the video cables (under normal operating conditions). If you read current in excess of what would be considered leakage current (i.e. you read more than 10mA or so) then there is a high chance that you have a wiring problem. Correct this first.

Q. The blue pair on CAT5 has the tightest twist and thus performs best to reduce noise.

A. This is indeed what we understood to be true however we are happy to be corrected. Joe Mosey of Belden is contradicting for Cat5 specifically, but in doing so supports our key message, which is that when it comes to wiring there are few if any standards; each manufacturer has different manufacturing methods

Q. CFL bulbs are actually WORSE for the environment because they cause electrical plants to work much harder. Its late so I forget the exact reason but it had something to due with the non-linear wave form and the heat it creates.

A. It’s all about the Watts (Volts * Amps * Power Factor) Basically stated, the utility companies have to generate and be able to deliver the Watts with the assumption that the connected load(s) power factor is unity i.e. voltage and current are exactly in phase. If teh propertied of the connected load(s) are such that voltage and current waveforms are out of phase (non-unity power factor) then the plant/generator produces more energy than is actually used by the device, and all the unused energy is dissipated as losses (heat). Note also that uncorrected CFLs are also worse for the consumer’s electric bill (since the utility companies generally bill us for apparent power)

Q. The fix is power factor corrected CFL currently associated with dimmable CFL.

A. When considering light bulbs, yes.

Please let me know if you need additional clarification on any of the topics discussed during the presentation?

Regards,

Marray,

Thank you so much for these responses and taking the time to reply. I think it will be referenced often.




Ernie-

Looks like we were both right. He did say it was the blue pair but that wasnt correct due to an overwhelming theme of the event that there is no wiring standard.

Murray, Thank you so much. We would love to have you stick around and check in from time to time. Your post is very much appreciated.

Does anybody remember the brand and model of the ammeter they used? It was a clamp-on ammeter capable of reading milliamps of AC current. When you ask people about such meters, as I did at CES, most of them want to talk about the maximum current and don't have a clue about minuscule currents like this.

Thanks.

Didn't any videos ever come of this? 

Those that attended, what standard installation practices are you changing or implementing based on what you've learned?

Any chance of getting a video for those of us who couldn't make it? It would be good to have it available to dealers, accessible through the MA site, requiring a dealer name and password.

For the video, I'd suggest that you email the person from Middle Atlantic who started this thread.