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Discussion Starter #1
I continue to field questions on several forums that indicate a great deal of confusion, fear, and misunderstanding with respect to power conditioning, surge suppression and battery backup systems. This thread will be dedicated to clearing up those misunderstandings and providing some pointers to best practices and value when choosing equipment to protect and optimize an A/V system.
 

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Discussion Starter #2
Surge Suppresors

It is my experience that surge suppressors can be very effective at protecting a system. I have found, in three decades of system design, installation, and repair, that there are some basics that are important. First and foremost are the importance of proper grounding and protecting ALL lines connected to the system. Most of the discussion assumes MOV based devices for a.c. line protection. I will mention series mode systems later, but these are often not appropriate for the average consumer.

A good reference for grounding:

http://www.hometheatershack.com/for...nce-information/7442-grounding.html#post62267

Examples of good values are listed below. Ignore the retail pricing and search for the current best pricing. Some of these can be found for much less sometimes. There may be similar models that are a better fit for your system. These are just examples of some of the better values that I have found. Please post links to any that you find that might be better choices.

http://www.panamax.com/Products/Floor-Models/M8-HT.aspx

http://www.cyberpowersystems.com/pr...?selectedTabId=specifications&imageI=#tab-box

http://www.tripplite.com/en/products...urge/index.cfm


Important factors to consider

Joule Ratings are not necessarily a good comparison. Some makers add the total energy that can be managed in all of the MOVs acros H-N, N-G, and H-G combinations. Obviously, there can never be a case where all of the MOVs are conducting simultaneously. Others rate the maximum for the largest capacity single path. There is no way to know how they do it from the specs provided. This means that two units with Joule ratings varying by a factor of 3 could have the same capacity to dissipate energy.

Current Ratings are a little better, though the same tricks may be used. Generally they are broken down, but many vendors do not even provide these numbers. The fact they are provided is a good sign.

Clamping Voltage is important, but most units don't really vary that much in this regard on the a.c. lines because most use similar devices. Again, if it is provided at all, it is likely a good sign. The voltages can vary greatly on signal lines, and again, many vendors give no specs at all. I tend to trust the ones that give the specs because it indicates to me that they at least think that it is important. The lower the clamping voltage the better.

UL Ratings are very important. Make sure that anything you buy has the UL1449 certification.

Signal Line Protection is very important. Make sure that the unit is specifically designed for the type of signals you are using. Some cable protectors may not pass d.c. back up the line. This will not work when using a power insertion for an upline amp nor will it work for sat systems that have to use the coaxial line to power the LNBs. Satellite lines usually pass d.c.
 

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Discussion Starter #3
Power or Line Conditioners

Lots of people are getting sold expensive power conditioners in recent years. They are a very profitable product for many retailers. I have found that many of them can be very effective in reducing line noise. The rest of the story, however, is that this noise is almost never a problem that affects the performance of your system. In many cases, users report improvements when installing them. Some of these improvements are real, and some are due to expectation bias or placebo effect. When an improvement actually does occur, it is often due to bringing all of the grounds in the system to the same potential when the signal lines are connected at the surge suppressor. The fact is, in most of these cases, that a much less expensive unit, or just improving the grounding in the system would have achieved the same effect. The dangerous part is that if the system is not grounded at the entry points to the home properly, surge suppression is less effective and the system may be at risk in the case of a severe lightning strike, power disruption, or surge.

The bottom line is, don't assume you need sophisticated filtering. Do the basics first and see what you can get for free (grounding), since this is important regardless of the purchase. Try a less expensive solution if problems remain, and only use expensive line conditioners if you must, or if you just want the cool lights and meters. There is nothing wrong with buying something because you think it is neat or it makes you feel better, but everyone should understand that most line conditioning is not going to improve your pix.

So why do I say that filtering noise is of little or no benefit? Well, modern electronics, with the exception of audio amplifiers, almost always use SMPSs (Switched Mode Power Supply). These supplies take incoming a.c. and rectify it and filter it like a conventional power supply. Then the d.c. is switched on and off through a transformer designed for this purpose at a rate of typically 50 -150 kHz. This creates a nasty looking pulse waveform that has to be rectified and filtered again to provide the d.c. that the various circuits need. After that, it is typically further filtered and regulated again. The noise on the a.c. line typically never survives the primary side filtering, and is even less likely to pass through the switching transformer. Even if it does, it is at such a low level compared to the switching pulse itself that it is insignificant. The rectifier and filter in the secondary will have to reduce this nasty switching pulse that is hundreds or thousands of times more energy to d.c. and filter its remnants. The noise from the a.c. line is simply not a factor. The rectifiers in the secondary of the SMPS are usually very fast recovery diodes, followed by capacitors and inductors to clean the line. It usually is then regulated again to provide the voltage that each circuit needs, and filtered some more. With SMPSs, there are also usually large inductors on the a.c. input to keep that noisy power supply from feeding back in to the power system and affecting other equipment.

So what about the line noise? How do we know that it can't somehow survive the conversion in the PS? All logic, theory, analysis, and reasoning is based on assumptions, and decades of experience has taught me to never rely solely on what "should" happen because you will probably have missed an assumption, or something that was believed to be insignificant turns out to be a real matter. So I look. I have lots of equipment in the shop, and some generates a good bit of noise, so I can often see noise on my bench a.c. lines with a scope. I also have a power line filter to provide clean power for testing. I can clearly see that it reduces noise over a very wide range of frequencies that could be visible in video. Looking at the a.c. before and after inserting the filter there is clearly a difference. But when I try to follow that noise into an actual power supply to a circuit, it just is not there and there is no difference with and without the line filter. There is one case where this is not true and I can see effects of power in actual video. That is when there is a ground loop, which with the complexity of the distribution system and various equipment in the shop can be easy to create. This is easily remedied by simply making sure that everything gets a ground with no more than a few ohms resistance to the a.c. system ground, or that all of the signal grounds are tied together. This is where I believe that most people's perception of improvements in their images with line filters come from. Tying the system ground together can be done without an expensive line conditioner, however. Even a cheap surge suppressor can do the same thing.

It would be a simple matter to measure noise ratios, dropout, or other possible effects of liine noise on video. None of the claims for improvements by line filtering systems come with the data to back them up. I know that I have looked for it, and I just cannot find the effect at all, beyond ground related problems that I mentioned above. It IS TRUE that line filters work to reduce line noise. It does not appear to be true that this noise has any visible effect, however.
 

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Discussion Starter #4
UPS

This whole class of products is an unfortunate mess, in my opinion. It should be understood that there is a big difference between backup power, surge protection, and line conditioning. They can overlap, but so many people buy products that do them very little good that a lot of education needs to go on in this business. Products vary so much that it is hard to generalize.

Battery backup itself is of no value to the protection of your system, except perhaps in settings where frequent outages occur. Even in those cases, there is likely to be no benefit to backup power over good surge protection. The danger is that many people think that their backup system is protecting the equipment, when in many cases the protection is incomplete or less effective than one might find in a much less expensive surge suppressor.

Many people have been scared into buying backup systems in order to keep fans running on lamp based projection systems after power interuptions. The fact is, though the industry won't tell you, that there is little need for concern for this. This debate keeps coming up, and many swear that they know better, but after much research, testing on a number of sets, and speaking to engineers and tech reps at manufacturers of TVs and lamps for years, I have concluded that this conventional wisdom is a big misunderstanding. It has been used to the advantage of the UPS vendors and retailers, but a smart consumer should not be misled.

One consideration that most people ignore is the long term cost and environmental impact of backup systems. The benefits, IMO, simply are not even close to the costs of having to replace units or batteries, then having to dispose of them over time. With benfits close to nil, the environmental impact of millions of dead UPS units and their batteries will be excessive and unfortunate.

My suggestion is don't bother with a UPS, but if you must, get one that is an online unti that regenerates a perfectly clean sine wave output and actually regulates. Overkill for most systems, but it avoids the problems with dirty stepped output and provides at least some regulatory effect.
 

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Discussion Starter #5
Series Mode Devices

Series Mode devices, such as Brick Wall or SurgeX are perfectly good for a.c. line protection. The can have advantages over MOV based systems. The problem with them is that they are expensive by comparison, and often do not contain protection for signal lines. The can provide better protection and filtering, but the filtering is simply not a real benefit in most systems. Not protecting the signal lines is simply foolish, in my experience. The argument for better surge suppression is similarly a red herring, IMO. The fact is that inexpensive MOV based units have proven to be very effective, and very robust. The claims that MOV based units tend to fail and have to be replaced is simply not borne out by field experience. In fact, they tend to be very durable and when they do fail, the better vendors often have lifetime warranties.

The bottom line here is that they do work, and are potentially better in many ways, but often have protection only on the a.c. line. The advantages are just not meaningful to most users.
 
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