Grounding your Gear – Saving Your System
What’s so good about good ol’ Earth? Well, for one thing, it’s huge, and because we are usually attached to it, electrically it’s considered the largest pole of most circuits. A good many electrical signals and power sources are measured with reference to “Ground”. We talk about the safety of a good and solid “Ground” connection. But what is it, and why would I worry about “Ground” with my home theater system?
Taking a quick look at what “Ground” really means, we find that it can mean several different things within the same general principle, which is that the planet we live on is at a reasonably stable voltage potential, and is used as a reference in measuring other voltages. Take that idea and extend it to equipment of all kinds, and Ground now is an electrical connection made to the outer metal cabinet or housing of equipment to limit the exposure of higher voltages to users. If the case is grounded, and something carrying voltage breaks loose inside, it will contact the inside of the case, and that voltage is taken directly to ground, away from our tender hands.
For home theater and audio enthusiasts, ground has several special meanings. One is, the common connection of audio and video circuits, usually the outer shield of connectors and wires, and is usually attached to the chassis of equipment. And the chassis is usually connected, via a 3 wire cord, to the third pin of an electrical outlet. That third pin may have an actual ground wire attached to it that runs back to the breaker box. That wire may be part of the sheathed wire in your home (if your local codes don’t require conduit), or an individual wire run back to the breaker box. However, the ground connection to the breaker box could also be carried by the conduit and metallic junction boxes. This is not ideal, but acceptable from the viewpoint of the electrical code. From the breaker box, the ground connection finds its way to actual earth via a ground wire and ground electrode, usually a long copper rod driven into the earth near where the electrical service enters the building.
One of the things we as home theater owners worry about is damage to our expensive gear from electrical surges. So, we pay all of $15 at the hardware store for a surge-protected outlet strip, plug our stuff in and call it protected. Or, we pay up for a fancy “power conditioner” with blue lights on the front, perhaps even a volt meter, that’s supposed to scrub that dirty power clean, and slam the electrical door to any wayward in-bound surges. It would be nice if it were all that simple.
There are a lot of signals that would just love to get to solid ground somehow. AC power is one, but probably the biggest, nastiest and most common of all comes from the sky…lightning strikes. These things are hard to deal with because they are buzillions of volts and even a strike nearby, not directly to anything in our home, can cause our sensitive equipment to vaporize silicon junctions in nanoseconds just from the electric field around the strike.
Taking a worst case of a direct strike to a power line feeding our house, that line (both wires of it) become momentarily energized to a voltage far higher than normal power, and with a burning desire to get to earth. Our normal power lines are purposely kept as far as possible from earth, and the things that stand between earth and the power lines are out gear, which make nice fast-blow fuses when hit with a lightning discharge. The only thing to be done is to offer that energy a much easier path to ground than through our gear, and an important part of that is a really good connection to ground. Think back to that ground rod some electrician pounded into the earth by your electrical drop, and imagine how good and solid that is. And now, think again. Not all ground electrodes actually provide good low resistance ground connections. In fact, some have shockingly high resistance (sorry!). What most ground electrodes have in common is that the owners have no idea if they are providing the best quality ground because the fact that they exist at all satisfies the electrical code, but nobody’s ever actually tested them. In lighting-prone areas like worst-case Florida, the likelihood of a good ground being required is quite high, but the conductivity of the ground itself may simply prevent that without special installation. The ground resistance of the electrode can (and should) be measured, and be as low as possible. Measuring ground resistance is also the only way to evaluate the primary ground connection, and how effective it might be.
So, assuming our ground rod has only a few ohms of resistance to ground, what gets that lighting strike energy to it and away from our gear? We need a good, low resistance path from the power line to ground…but that can’t exist because, well, that’s a short circuit, and nothing would work that way. The magic devices that exist in most surge protectors are MOVs (Metal Oxide Varistor) also known as a VDR (Voltage Dependent Resistor). These things are meant to be very poor conductors (insulators) up to a certain design voltage, then wam-o, the become like a dead short, shunting current caused by a high voltage spike away from protected equipment. Hopefully, the spike is short and moderate, but if not, the MOV/VDR will sacrifice itself, perhaps having protected the gear, perhaps not. That little red LED on your Home Depot power strip is meant to indicate that the MOV/VDR is operational.
Now, to fully understand the problem, consider the two basic types of surges. One is transverse, meaning they occur between the hot and neutral conductors of a power line. They are caused by switching large electrical loads like motors on and off, and can come from inside or outside the home. The second type of surge is “common mode”, or arriving at the device on both hot and neutral wires. These types of surges require two more MOV/VDRs for protection. Some common-mode surges can be quite high, thousands of volts. Then there’s the lightning strike, which goes beyond any of this.
What’s wrong with your surge protector? Perhaps a lot, if you consider that even expensive “power conditioners” require a really excellent ground for good protection, and probably aren’t getting it. An excellent ground is obtainable at the end of the ground wire that connects to the ground electrode, assuming low ground resistance. But, once we move away from the ground bus in the breaker box, the little 14ga wire, or steel conduit offers much less than ideal ground connection out at the equipment location.
So what to do? The only, and I mean ONLY reliable surge protection system for your home is the “whole house” surge protector installed at the breaker box, attached to the incoming electrical drop, and ending up at the ground rod. Nothing else works as well, and some token surge-protectors are basically worthless. Don’t let that $20,000 equipment replacement warranty fool you either. The fine print is usually not available, and once it is, you find out why those “insurance policies” are never paid out.
What about filters? In theory, the voltage surge that hits you is very short in nature, yet very high in voltage. What if we were able to filter off most of the high frequencies found on power lines with a big honking magnetic filter? Turns out, that does work within limits. The filter simply won’t pass high frequency energy, and that leaves MOVs down stream of it with much less to do.
What about the audible and visual benefits to squeaky clean power? You know, funny thing about AC power, nothing actually uses it directly. Every audio and video device, have takes that raw and nasty AC power, transforms it, rectifies it, filters it (yes, filters it), regulates it and the, finally, it’s smooth clean DC that can be used by the device. So lots of changes going on in the power supply that sits just past the power cord, and included in that power supply is an all-important filter. That filter, mostly a large capacitor, is there specifically to kill all noise on the rectified DC. Mostly that noise is 60Hz and 120Hz from the power line and rectifiers. Those are pretty low frequencies, and to deal with that the filters have to pretty much kill those frequencies and everything above. Job done, right? What about the high-efficiency “switching” power supplies? These are now very common, and work very well. They convert AC power line voltage to smooth clean DC using high-speed switching techniques. Those techniques by their very nature produce high frequency noise by the ton, and so they must have, and have extensive output filters. See where we’re going here? With filters on analog and switching power supplies in place by necessity and design, how on earth would slightly filtering the AC line do any better? It doesn’t, and claims of improved picture and sound are imaginary in all but the rarest cases.
“Now hold on there”, you say. “When I connect my computer to my DAC or AVR, I get this horrible noise, I’m sure it’s coming through the power!”. Well, sort of. Some computer power supplies, particularly the laptops and cheaper units in general, impress a rather substantial amount of noise on the ground connections, which may be shared by an audio device that references its audio signal to that ground. Adding a power conditioner with its noise filter will likely do nothing for two reasons. First, the filter is on the incoming line, and the noise generating power supply is on the opposite side of it, with its ground shared by audio gear. Second, many conditioners don’t bother filtering the ground anyway. There is a simple cure for this problem, but…well, not in this post.
So, what do we need most to protect our gear? I good low resistance ground electrode, and a whole-house surge protector. That’s it, that’s all, nothing more. If you want to add a power conditioner for aesthetics, voltage monitoring (why, exactly?) or power distribution within a cabinet or rack (perhaps the best argument for a power conditioner), that’s fine, but it won’t help your sound or picture, and won’t provide definitive surge protection for your gear.
As always, contact Platinum Home Theaters for grounding, and surge protection solutions.
This added final thought: Local plug-in surge protectors are not without benefit, as a great many surges come from within the home, though these are typically less intense than those from outside. Cascading surge protection (Main breaker panel > local plug strip) is not a bad idea at all. The problem with the surge protector plug-strip or power conditioner is the tendency to rely on it alone. Start with whole-house protection, then add the local plug strips, and you’ll be about as protected as you can be. Don’t forget that even plug strips come in the surge-only version and the filter + surge protection version. The latter costs more.
Ignore that $$$-equipment-replacment warranty. They rarely pay out.