Power, Conditioning and Grounding

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.

…and that’s why I hardly go to movies anymore

Just got back from “Jobs” on the big screen, AMC Yorktown.

The pre-movie ads and videos are projected using a low-resolution, dim, probably analog projector with rolling hum bars moving up the screen, soft focus, low contrast.  The sound was so sizzlingly bright I wanted to stick fingers in ears.

Then the curtains open, they kick on the big projector.  Rolling hum-bars are gone, it’s a few foot-lamberts brighter, but not much really.  Sharper for sure, but the illumination is very uneven, with a hot spot in the middle, dark corners, etc.  That’s just sloppy operation and poor maintenance.  The sound was left heavy, indication a mis-calibration of at least one channel level.  The dialog was dull, could be a production issue, but more likely calibration again.  And they never did quite get the house lights all the way out, so the blacks were dim orange, doubtful contrast hit even 500:1.  20 minutes of trailers and ads, at least.

And I have not one of those issues in my home theater…you probably don’t either.

So what was good?  The subwoofer response in the theater was almost barometric, really went low, but was probably out of cal.  Just a bit too much of a good thing.  The screen size was impressive.  The seats were comfortable.  And we had nearly a private showing.

A couple quick words about “Jobs”.  The personalities were most interesting, and the story was too, but there’s a lot of board-room talk and politics.  About 3/4 of the way through the movie Steve was just getting the axe from Apple, and I was wondering how on earth they would finish this up in 20 minutes.  Well, they didn’t finish in 20 minutes, and in fact didn’t finish the story at all, but the highlights were hit, and the physical resemblances were startling.  Worth a view, probably wait for it on iTuAmazoFlix.

A Leap of Faith

We always have our eye out for technical advancements that we can bring to our customers to make their life easier, better, or more fun.  So, when I saw a promotional video of the Leap Motion controller back in February, I decided to pre-order one and evaluate it for use in home automation, control systems, and media servers.  It took months, but I got it.

leap

Leap Motion looks like the first step to having those cool transparent, touch-less, interactive computer screens we’ve seen in Iron Man and Minority Report in our own homes.  The idea of using hand motion to direct movement of items on screen is, well, magical.  And that’s what the thing is…magical.  Point your finger and move the cursor.  Swipe with several fingers and whip screens aside, zoom in or out, scroll up or down.  The Leap App Store has dozens of free and paid apps that demonstrate the strengths of the device.  “Flocking” is probably a favorite, as you can use both hands to direct schools of digital fish.  Even the test visualizer is pretty nifty.

So I set down to see how Leap Motion would work as a real controller.  My extended idea was an LCD screen on a glass wall that a home owner or executive would use his hands to browse the web, or interact with his media server.  But to test it, I just needed it to work as a touchless touch-screen, or an air-mouse.

One thing we need from pointing controllers, mice, touch pads, etc., is precision. Nothing is quite like the frustration of a cursor moving randomly around the screen, or missing your click target. Today’s optical mice are very high resolution devices, and every one of them has a software control that lets users adjust the speed of movement, plus other things like click speed, pseudo-inertia, etc. So, we got our precision, and flexibility, and for most of us mousing and clicking is done without thought, the cursor becoming an extension of our hands.

So not having to touch anything and move the cursor…now that would be special. And it would be if the Leap controller was a fully baked product, but it’s not quite cooked enough. As a pointing device, the precision is poor, cursor speed doesn’t match your pointing finger, and clicking is achieved by crossing an invisible threshold in the air, close to your body you’re moving the cursor, crossing the threshold and you’re clicking. Gestures like five-finger swipe can be set up to do things too, so swiping between apps and browser tabs can work, as does scrolling…sort of.  Pointing to the little “Prime” box on Amazon’s search pages becomes a game, so long as you can upload that mindset to your brain.  If not, it’s pure frustration.

The device also gets warm…almost hot. It plugs into your USB port, and uses a standard diameter cable with a non-standard connector on the controller side. It comes with a long cable and a short cable, but what it should have, in these days of wireless mice ($12 at Walmart!) and Bluetooth, is no cable at all. That would clearly be a battery project, with apparently quite a bit of current drain, which ends up as heat. So for now, it’s cabled, and hot.

When we bring new devices into our environment, we don’t really want to cater to the devices needs, we want it to just fit in. The Leap Motion controller is a bit more finicky, and is bothered by high ambient light. Getting it too close to your monitor down-shifts it to a somewhat ambiguous reduced-performance mode indicated by a yellow light in your tray or menu bar.

Because the controller looks upward over a 45 or 50 degree angle, you can’t work too far above it, or too close to it, or too far to one side or you leave it’s control area. For it to interact well with your screen, it should be reasonably centered. If there were a cursor speed control, distance to the screen wouldn’t be so much an issue, but for now, it’s too fast for me. So, for me, a MacBook Pro 15″ user, the idea position for the controller was dead in the middle of my keyboard, a place I have to use for other things…like typing. And, if you get it too close to your screen, it chokes on all that extra light. I have no idea what it would do in really bright light.

In truth, it would probably take a lot more getting-used-to than most users would tolerate.  Things like launching an random app by reaching for a pencil, or putting your computer into screen-saver mode with your elbow might sound humorous, but the humor wears thing quickly.

The concept is sexy, the packaging is pretty good, but until it works seamlessly with existing systems, in existing environments, it’s more of a work in progress.

I wish Leap Motion the best with the project, and look forward to testing an update, perfected version.  This is something we want to work, and when it does, it’ll be wonderful.  Until then, the leaping you’ll do is out of frustration.