UPS for A/V use - AVS Forum
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post #1 of 6 Old 12-18-2000, 07:01 AM - Thread Starter
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In general, my utility power is outstanding, but living in a relatively rural location has one drawback. My power comes in via overhead poles. This weekend, we had a horrible rain storm, accompanied by very high winds. I suppose the good news is that our power didn't go out. But the bad news is that we had a series of 2 second long power hits which occurred at random intervals through Saturday night and Sunday morning. Big problem if your are watching Gladiator on your brand new Dwin! I am assuming that the surge protectors choked off anything that might have done any real damage, but the on/off cycling must be terribly hard on the projector and amplifiers!

Does anyone have experience with using UPS systems on A/V equipment? I'm looking for a quiet, online (non-switching) UPS, which has the ability to supress surges, but can passthru when the equipment demands more juice. There are lots of computer oriented systems out there, but I haven't find one with this sort of spec.

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post #2 of 6 Old 12-18-2000, 09:35 PM
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UPS systems are generally designed to deal with voltage sags and spikes. They generally don't work well for extreme lightning related strikes. I've heard of lighting strikes burning out the parts which control the spikes, and due to the higher voltage then jump the gap and fry the UPS, and equipment as well. (Figure if lighting has enough voltage to arc a couple hundred feet from the sky to the ground, it can probably jump that extra inch or so inside the UPS.)

That being said, having a UPS installed, can provide an insurance route to replace your equipment after it's whacked by a lightning strike.

Here was one link that came to mind: http://www.bestpower.com/products/pa...ii/product.htm

Also, don't forget to make sure any phone lines hooked up also have some sort of lighting protection as well. (DSS?)



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post #3 of 6 Old 12-19-2000, 04:02 AM
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Couple of thoughts:

-Most good UPSs have high quality surge bar type protection built into them, wired before their own electronics.

-The PowerWare 9 Prestige line is a product that I've been wanting to investigate for home theater use. It is a true on-line UPS meaning that the electricity is always going through the AC/DC/AC conversion. So in addition to a little run time in the event of power outage (or sags, or surge) you are getting a built-from-scratch clean sine wave. The specs (harmonic distortion etc.) are not in the same class as the PS Audio stuff, but VA for VA (watt for watt) the price is substantially less. www.powerware.com

If I can get one from them to try, I'll let you know how it goes.

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[This message has been edited by Brian Florian (edited 12-19-2000).]
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post #4 of 6 Old 12-20-2000, 08:14 PM - Thread Starter
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Brian:
The Powerware UPS looks good, except for the noise factor...45-50DB...ouch! That would require a hush box, or perhaps locating the UPS remotely from the theater.

I've been giving some thought to a Compaq T1500 or T2000. It's a line interactive ups, so not quite as clean as a double conversion system. But they don't seem to have any fan noise.

I'm also concerned that none of the available systems seem to deal well with dynamic loads. They are all tuned for computer applications, which tend to run hot and steady. Put an ammeter on your amp during U571, and see the difference in an audio application!

It would seem that there's a market opportunity for someone here. A PS Audio type product with a battery backup would be perfect. Pass me my soldering iron!

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post #5 of 6 Old 12-23-2000, 01:55 PM
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I have an American Power UPS hooked up to my system. My Sony 7000 DVD looses it settings during lengthy power losses that made me finally hook one up. No UPS can totally protect you from a lightning hit, but it certainly can protect your equipment to some extent.

The other nice feature of a UPS is you don't loose your VCR recording schedules. Now that I added a Replay 3060 to my system, momentary power losses would not be good for a hard drive when writing data.

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post #6 of 6 Old 12-23-2000, 07:39 PM - Thread Starter
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Let's try to get on the same page with some terms & concepts. The following is my best understanding, and I ask to be corrected if I'm off base:

First off, there are three common types of UPS systems:

1) Standby systems. Where the battery is kept charged and ready, but not connected to the output circuit (unless an outage occurs). This is the cheapest type of UPS, there are almost no products in the market using this topology. The ones that are, are usually the ones that are built into a power strip, and cost under $100. They use crude switching inverters, which produce a modified square wave. They may not be compatible with audio electronics, especially if any line conditioners are used downstream.

2) Line interactive systems. A transformer with a large ferrite core is used to maintain power during brief voltage drops, and to provide some degree of line isolation. The battery and inverter function during extended outages, and can supplement line current during brownouts. The electronics typically provide buck/boost control to keep voltage within relatively tight tolerance. These can be thought of as a combination of an offline UPS with a line conditioner/voltage regulator in one unit. Inverter electronics are usually better than simple standby UPS units, producing a realtively clean sine wave.

3) Online, or double conversion UPS units. This is the kind often used in data centers. The input current charges the battery, the battery drives the inverter. In effect, the load is always running on battery power, totally isolated from the line. These units are usually more expensive than the other types, and have good inverters. They are the most applicable to video and audio use.

I have yet to find a UPS of any description or price which doesn't meet UL and CSA standards for surge suppression, which is more than I can say about many of the audiophile power products out there. I'd consider any of these devices as good as any suppressor in the market. Ground mode events may occur with UPS units, but they are as likely with any method of suppression available. I have to think a bit about line isolators and balanced power systems, there may be something to that argument.

One of the big drawbacks to all UPS systems is the quality of the inverters used. Typically, they quote a 3% THD, but if you read the fine print, the THD increases to 6% under a non-linear load. That is to say, they are optimized for computers, which draw a steady current. They potentially can produce audible effects, especially if they are used on your amps.

Just for contrast, the PS Audio units have very little THD They achieve this by playing a hard coded sine table through a quality D/A converter, and use the output to modulate rectified line current. The result is a very pure sine wave. Of course, they do nothing in a power outage, but someday someone may use the technique to build an audophile UPS.

Another problem with UPS's is audible noise. All the electronics produces gobs of heat, and any UPS of size carries a fan. Since they are made to run in a data center, where nobody cares about a little noise, the fans produce anywhere from 45-55DB. And to think I bought a fanless Dwin to keep the room quiet!

I've come across a Compaq T1500 which I'll be able to borrow in a couple of weeks. It's a line interactive UPS, similar to an APC Smart UPS. It think that this might be the best compromise: when the power is good, it will act like a line conditioner, surge supressor and voltage regulator. But the waveform will essentially be determined by the input current, except for buck and boost conditions. When the line is cut, it should produce inverted battery power smooth enough to carry the system briefly, and allow me to shut down smoothly. I thought it would be fanless, apparently Compaq just doesn't publish a spec on audible noise. If it works, I will consider using a similar hardwired UPS on my A/V circuits, and locating it near the panel, so that I won't have to listen to the fan. I'll report back on my experience.

[This message has been edited by MFrank (edited 12-23-2000).]

[This message has been edited by MFrank (edited 12-23-2000).]
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