I feel as though I have traveled back in time to the 1980s when I worked as an installer for a very famous high end salon in NY--one of two stores who had on display Infinity IRS ( the other was on the wrong coast ). The attitude was that you did not need to know anything, only have "ears." In fact, the more technical knowledge you had the less valuable you were.

I do not have an EE. My degrees are in American History so if I have learned this so can anyone else. The mathematics can be complicated but distilled down to basic English it is not really that complicated. If you are in the custom installaton business you should understand Ohms law; you should understand basic electronics; you should have basic understanding of RF, you should know what causes gound loops and how to trouble shoot them and understanding what a voltage divider is should be expected. There are more than enough classes at CEDIA that can help. Various manufacturers have classes-where they push their products- but provide information to solve various problems typiclly encounted in our business. Eric Johnson when he was at Niles was one of the best at this as was Frank White when he was with Channel Plus. The idea that an electrician has any understanding of anything, including how not to electricute himself, should be postulated. In law a defense based upon ignorence is not acceptable. How can one defend ignorence and predicate that defense on not being as intellectually challanged as an electrician?

If you " design and install home theater systems" you are interconnecting a variety of systems and sub systems that will show evidence of ground issues at some point. Some of this will be the result of equipment connected on different electrical phases. Some of it because of eddy currents. Some of it due to different ground reference points ( such as ground blocks at the drop ), some of it due to stray voltage on CATV lines, and some due to dirty neutrals. I was never a "roadie" but some of the best techs are. Why? You build the system, trouble shoot it and fix the problems and you learn to do it very quickly. And the first thing you do before you go on the road is build the system and find and isolate all gound problems. As a home theater designer you should know more than an electrician about electrical theory and practice, although you may not need to know how to bend pipe, install "madison clips," balance phases, know how to wire a buck and boost transformer or how to wire a 4 way switch. The idea that all you need is the knowledge to convince people to purchase esoteric and high priced equipment is shocking to me. I have worked very hard to learn my craft and that craft is to be a professional custom installer. You should know electrical engineering theory to some degree. You should know why your equipment needs to be on the same phase and you should be able to explain to sparky why. Ground loops are hardly difficult to understand and even more simple to fix. There is a ton of information on this if you take the time and have the desire to be to learn Arrogant? Damned right I am arrogant. If I can learn this any of us with the desire to learn can.

For those who wish to learn try this link: there are a batch of useful information contained in the white papers.
[Link: jensentransformers.com]

And take Bill Whitlock's course on grounding. Studiocat is correct. These are the best and there is sound engineering behind them. This is not to say that the Leviton product is not well designed. I have not looked at the specifications and I am not passing judgement on it. The idea that any of us would not bother to learn why a product worked and just install it because it worked is mind boggling to me. And to proudly claim that I do not need to know because I am a home theater designer.........

The more things change they stay the same. Just like the famous audiophile salon I began my career.

Alan

Recapping:

Two common sources of hum:

1. Cable TV.

Solution: Isolate with a pair of transformers back to back, etc. Routine.

2. Differences in ground potential at different outlets in the home due to being on different panels, breakers, etc.

Preferable solution: Try to tie TV to same outlet that equipment stack.

Secondary solution when preferable not feasible: Use an MIW Power, Leviton, etc device in the wall.

I think this might be what I have gleaned from all the posts. I've done service calls for nearly 30 years and have frequently run into cable TV ground problems, but haven't dealt with enough plasma to have run into and solved those problems yet. Wasn't a problem with projo or direct view, obviously.

Thanks to all who have shared their expertise.

=Tom

I feel rather insulted by your comments Audible Solutions. I am not the person selling high end gear and have no clue how to hook it up. I pride myselk on being the best that there is. I live, breathe, eat, and sleep with this stuff. I understand ground loops. I understand that the entire A/V System must be on the same gorund. When we do our high end theaters with front projection or plasma, we have our electrician wire the room, and he uses one or two circuits. This is probably why we don't have a grounding problem. I do understand Ohms law. I was a service technician for four years. I was factory trained by Toshiba, RCA, Sony, etc.

When you have a house that is built, and there is no way to properly ground the system what are your options? 1. properly ground the system (Which could be very costly if the house is drywalled, plaster lathe, etc.). 2. cut the ground prong off the cord (Which i have never done, but seen almost every other company in the city does it) 3. use a leviton, jenson, panamax, etc.

Just my two cents.

Mike

1. You specify to sparkey that all circuits in the theater are on the same phase. In a large home with centralized and decnentalized A/V equipment this can be difficult so you plan for solving gound problems because you know that sparkey either cannot or will not place all of your outlets on the same phase.

2. When you have a gournd loop you find out what is causing it.

3. Good practice is not to depend on the cable company's taps and intall a Jensen transformer ISOMAX CCTV isolation transformer. Expensive but not that expensive and you solve the CATV problem and there are no return path issues.

4. If some other method is discovered you take the time to find out how it works. The panamax Kludge is to ensure that all AC for products is on the same electrical outlet. Even sparky can bring a dedicated circuit to the equipment location and jump it to the display location. If you like selling the product feel free to do so but you should understand how it works. I have still not had the time to look at the Leviton product to determine what it is doing. But if you use it you damn well should. I know how isolation transformers work and when and why to use them.

It's called being professional. No one is asking anyone to prove the Schrodinger equasions. This is easy, simple and straight foreward. But I guess I am a jerk. So call me a jerk for assuming that professionals behave professionally. And understanding what happens and what to do as opposed to using black magic and throwing matterials at problems seems like the professional approach. Half the time, even with the theory, we are still parts swapping anyway. There should be some knowledge behind anything we do.

Alan

Hey Alan,
Your expertise is good and thanks for sharing it.

You have to assume that some of us can't research every single thing we do. Each of us with business, family, hobbies, etc have to balance these and each man allots a percentage of his time differently.

If I wanted to put everything aside and dedicate 100% of my time to my craft then I would know everything there is about what I do. I am not able to learn every theory with the time I have available.

So we have to pick our spots. We get neck deep in some spots and dip our toes in others. That means we are true experts in some areas and know how to make things work (still using professional products and accepted trade installation standards) in others.

With the limitation of time, that's what most of us probably do.

=Tom

I also have a family with 2 children with whom I spend too little time due to my chosen profession and manufacturers who make conducting it difficult. The irony here is that ericstac had traced the problem back to the cable box only he did not know that was significant. Fine. We all need a little help now and then.

But to provide a reponse that essentially states that I am not an electrician but a home theater designer and therefore have no clue why something works or why I am suggesting others to use it is......unfortunate. I am hardly the sharpest tool in the shed. Just ask THON. So I use time in place of native intelligence. The information is out there if one cares to amass it. The fact is that we are in business that requres us to know a little about a lot of systems. from networking to electrical to RF, to acoutics. Since this is our profession should we not become competant at it? Or are we to become little different than our electrical brethern and no little about anything. Basic curiousity over time would have led me to look at the specs for that Leviton piece. I am programming now ( taking a break ) but some time this weekend I will visit Leviton and see what the specifications are. Trouble shooting ground loops requires time, patience and some organization. You do not need to be very knowledgable about much of anything to solve it. Yes, even an electrician could do it--and since he is usually the source of the problem it should be his problem to fix. NOT!

I hold everyone to the same standard I hold myself. If I can learn it anyone can. No one is designing circuitry or solving for x.

Alan

Just for kicks. I just worked on a Runco Projector today that would not turn on. We go over to the projector it does not power on. Turns out that an extension cord w/o a ground was run 15 feet through the ceiling, then hooked up to an outlet. This was in a very expensive home theater put in by a very prominent company in the Cincinnati area. This is terrible. We do not do this type of work.

I am a professional. I understand that when you have a ground loop problem, to correct this problem 100% you should ground the display device to the same ground as the equipment. what customer is going to pay the time to run a new ground? No customers that I have. I have had great success with the leviton and will continue working with it.

Mike