Secrets Q & A

Power Protection: Fancy Power Protector or UPS or Simple Surge Protector?

Question:
I just bought a Samsung UN65F8000 LED TV, a Piooneer VSX-1128-K receiver which will power a pair of polk audio RTiA1's a CSiA4 Centre and PSW10 Sub. Also in the setup is HD Satellite box, a PS3 and a PS4 when it arrives in three weeks along with a BoxeeBox and some other crap. My question is about power protection. Should I get a fancy power protector for several hundred dollars, a UPS or simple surge protector? I don't mind spending a few hundred bucks if it will serve a purpose. Our power isn't bad but goes out acouple times a year and we get a brown-out now and again.

- Jack M.
Halifax, Canada

Answer:
When it comes to protecting our equipment from power related events, what you need or deem appropriate will come down to the general risk in your area (how "bad" your power is) weighted against your risk tolerance. If you live in the Midwest where lightning storms are frequent, then protection from catastrophic power events would seem wise. If your power is notorious for cutting out, or worse cutting in-and-out, additional protection may be a sound investment. If on the other hand you can't recall the last time you had to light a candle, then investing hundreds of dollars on an elaborate UPS system might not make sense to you.

Let's look at what can go wrong with power and what we can do to protect equipment.

Spikes and surges are terms used to describe a brief but dramatic overvoltage, spikes being VERY brief (as short as a nanosecond or as long a microsecond), surges being somewhat longer (from a microsecond to several milliseconds). Spikes and surges can range from a few hundred volts to several thousand. A lightning strike or a blown pole transformer are classic examples of causes yet, while somewhat less dramatic, spikes and surges can be caused by seemingly benign sources like a big power tool being turned on somewhere else in the house.

Protection from spikes and surges is rather simple: Good quality "surge bars" from brands such as TrippLite whose sole business is power are designed precisely for this. Almost all employ metal oxide varistors (MOVs) as the key component which deflect excess voltage to ground. They are often accompanied by a fuse and a few basic frequency filtering components (chokes/capacitors). The thing to know about surge bars is that they only address those very short but dramatic spikes and surges. A common misconception is that they somehow regulate, or at least suppress the voltage to a perfect 120V. They do not. Any UL listed surge bar will essentially be benign until 330Volts (the so called "let through" voltage") which equates to about 220Volts RMS. Don't go looking for a powerbar with a lower let-through rating: not only is 330 the minimum for UL, if one did build a surge bar with lower let-through MOVs, they would constantly be shunting to ground and fail prematurely. Remember that in North America our 120Volts is RMS, the peaks being about 170Volts…and that's when things are perfect. It's natural for voltage to swing a little throughout the day.

Note that for "complete" protection one needs to have every wire feeding a system covered. This can include the oft forgotten coax from the cable company, copper lines from the telco, even the satellite dish connection. Though the risk factor on these "data lines" is something which is debated, if you are considering a surge bar and you want to go the distance, look for models with all the connections you will need.

But what happens if a mild (sub-330 Volt) overvoltage, or undervoltage for that matter, comes along and lasts not for milliseconds, but several seconds? These would be termed swells (overvoltage) and sags (undervoltage, colloquially known as brown outs). Have you ever noticed your lights dim, or perhaps glow bright for a few seconds right before the power goes out, or cuts in and out? Surgebars do NOTHING for this type of power anomaly which does indeed have some damage potential. There are two types of products which offer protection: Line Conditioners and the venerable UPS or Uninterruptable Power Supply.

Line Conditioners are simple multi-tap transformers which will either step-up or step-down the voltage when it reaches certain thresholds. They are somewhat more effective on swells than they are on sags as even though they can step the voltage up, available current is correspondingly diminished.

In most contexts UPSs, which essentially are a big battery, are meant to keep equipment going during an outright power failure, but by proxy they represent something of a holistic protection for just about any piece of electronic equipment from just about any power event. Their function is quite simple: in addition to basic spike/surge suppression, when the voltage goes above or below a certain threshold, the UPS switches the equipment off the wall and onto battery, providing the equipment with a nominally correct voltage. Note though that not all UPSs are created equal. The most basic are termed "standby", characterized as a begin presence until the voltage deviates quite far from the norm (or cuts out altogether) at which point they switch to battery.

The next best topology is termed "line interactive" which is a sort of hybrid between a Line Conditioner and a UPS: within a certain range they will step the voltage up or down, going to battery only when outside of the range they can effectively correct without doing so. The last and ultimate UPS type is termed "Online" (or Double Conversion) where the equipment NEVER sees the power coming from the wall at all: even when the power is on and normal, the attached equipment is run off of the UPSs DC-to-AC converter so voltage never varies, and the response time of the UPS is essentially zero. The equipment gets picture perfect power 100% of the time.

Before everyone runs out and buys their home theater a UPS, there is another aspect of UPS topology we need to touch on: the quality of power they put out when on battery (or in the case of the OnLine UPS, all the time). The vast majority of UPSs will output a stepped-wave (also called PWM sine wave). It's like outputting digital audio data instead of putting it through a digital to analogue converter. This sort of power is not ideal, but it works well enough for equipment which employ their own AC-DC power supplies. For some equipment though such an AC output can actually cause damage or malfunction. Better UPSs will have a so called "true" sine wave output with almost universal compatibility, recommended for everything from sensitive servers to refrigerators.

Virtually all Stand-by UPSs have stepped-wave output. Line Interactive UPSs may be either stepped-wave or true sine wave, while practically all OnLine UPSs have true sine wave output.

But wait, you still might want to hold off on the OnLine Double Conversion UPS with sine wave output. While true sine wave is better, the quality of the sine wave itself, like the output of an audio DAC, will have a certain Total Harmonic Distortion or THD level. While the levels are low enough for most gear, with particularly sensitive AV equipment (especially pure analogue) THD in the power can reach a level which may manifest itself in the audio and/or video. This really isn't an issue with a Line Interactive UPS since you will only be running off its inverter briefly during power events, but in the case of an OnLine UPS with its always-on inverter, you'll want to make sure it has a nice low THD.

The other consideration with UPSs is cost: it is directly related not just to the quality of the circuitry, but to an even greater extent the capacity (simply stated, the number of things you can plug into it). Providing UPS protection for a high end audio power amplifier is going to cost you more than the $60 "office UPS" you see in the sales flyers. Be prepared to pay $500 or more for a quality line interactive sine wave output model which can match the capacity of a 15amp household circuit, or almost twice as much for an on-line model. One last, but rarely looked at, aspect of any UPS is noise: most good UPSs, especially the higher capacity models, will have a cooling fan of some sort. These can range from inaudible during normal operation, to unacceptably loud all the time (most OnLine UPSs fall into this last category). There are some UPSs marketed specifically for Home Theater use. These tend to have a curiously higher price tag, but unlike their "server room" counterparts will have relevant data-line protection included, and by definition should be among the quietest.

In summary a basic but good quality surge bar from a company like TrippLite or APC will run you well under $80 and as such is a sound investment (at very least it will facilitate power hookup for a system with many components). Beyond that it is a question of how bad your power is, and the cost of more elaborate protection against the value of the gear you are protecting.

I live in Atlantic Canada and have my home theater equipment on a good surge bar, nothing more. My brother, who lives in the greater Chicago area, has almost everything in his house on a UPS of some sort. His home theater gear is on a 1500VA line-interactive stepped-wave output model. He hears the loud click of its relays at least several times a week, each one an indication that his power is bad enough to warrant using a UPS in the first place!