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Discussion Starter · #1 ·
Hello all.


I plan to use a UPS with my receiver.


But a friend of mine forwarded a theory that he'd heard about it being inadvisable to use a UPS on a Receiver due to complications that can arise with the UPS trying to drive the amplifier section. Is there any truth to this?


Can a UPS be used with a Receiver, provided of course that the UPS can handle the full load of the Receiver?


My Receiver has a power consumption rating of 600W and I plan to use a 1500VA (1050W) UPS.


Any information would be much appreciated.

Thanks in advance.
 

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A UPS does not necessarily provide a clean sine wave ac power source, typically they are designed for computers. Computer power supplies completely reform the incoming electricity into DC voltages to power the PC components. A power supply in a piece of audio equipment, although some filtering is done, usually use a torroidal transformer to develop higher rail voltages to the output devices. This is two very different applications. A UPS may actual cause damage to your audio equipement. Also, do not mistake a UPS for a line conditioner. A conditioner actually controls the shape of the ac voltage, it can eliminate spikes and irregularities, but typically not operate as a backup device in the event of a power outage.

You could test it with your equipment, but it would not be universally advisable to use a computer type UPS with audio equipment. Just my $.02
 

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Discussion Starter · #4 ·
Thanks for the advice.


Certain "upscale" UPSs apparently DO act as line-conditioners as well, whenever the AC power is available. During a power outage, it then resorts to battery power.


In any case, on the advice of Johnla, I will e-mail APC as well and see what they have to say. I only hope that they don't tell me that there won't be a problem just to ensure that they sell a product!!
 

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I don't think APC is the kind of company that would recommend a product that is not suitable for the job it is asked to do, just to make a sale.

I may be wrong, but I think that they will give you a honest answer when you ask them.
 

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Discussion Starter · #6 ·
I wrote to APC asking about my requirements. Given below is their reply, for anyone who may have the same concerns I did. I must say APC responded very fast and seem to be most helpful.


I wrote them this:
Quote:
I have a Home Theater Receiver that consumes 600W (max) and a powered subwoofer that consumes 350W (max). I was contemplating on using a 2000VA UPS with this system.


I would appreciate if you could clarify the following for me:


1) Is it alright to use an A/V Receiver with a UPS?


2) Are there any associated problems with this combination (e.g. Inability of the UPS to handle peak levels, etc.)?


3) Is it alright to keep the UPS On-Line 24 hours of the day without ever switching it off? In order to keep my home theater system on stand-by, this is what I would have to do.


Thank you very much for your time.


Sincerely,

Manendra Pedris.


And, this was their reply:
Quote:
Dear Valued Customer,


Thank you for contacting APC's electronic support on 09/11/2003 03:37 PM regarding your inquiry. I would be glad to assist you.


Allow me to address your questions one at a time:


1. Yes. Using a UPS to provide back up for a home stereo is very common.


2. Electronics such as amplifiers have large capacitors, which need to charge up when you firs turn on the unit. This results in what we call an "in-rush current". Therefore, if you are planning to turn on your amplifier while the power is out, the draw will momentarily exceed that 600W rating. Therefore, we would suggest a unit capable up supporting at least 900VA for that amp. With the subwoofer included, you will want to go with at least a 1400VA unit. Therefore, the 2200 would be an excellent choice.


3. There is absolutely no problem with keeping these units on 24 hours a day. I would say 99% of our customers leave them running 365 days a year.


Although the SU2200NET would be the preferred choice, the input plug on that unit is a round 30 amp twist-lock plug, which would require installation by a licensed electrician. Therefore, you will most likely want to go with an SUA1500. I am very confident this unit will be able to support your equipment without fear of overloading, and the input is a standard 15A plug.


Have I satisfactorily answered all of your questions? If not, or if you have any further questions, please do not hesitate to contact me by responding to this incident. It would be my pleasure to ensure that your issue is quickly resolved!


Thank you for choosing APC!


Any comments, people?
 

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Nope, the APC response was pretty much spot on, as well as mpedris's remark that certain UPSes do functional as line conditioners. A lot of amps are designed to minimize inrush, you might want to talk to your amp manu. and see what they say maxiimum power consumption is like when it is turned on. I wouldn't worry too much about it as comptuers are the same, the require more current to turn on than when operationg normally becuase they must spin up all the disks (which is why large SCSI arrays allow delayed spin up based on SCSI ID).


Doh, I'm a moron, you are mpedris!
 

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Discussion Starter · #8 ·
Apart from APC, what are other good UPS manufacturing companies?


Does anybody know of any UPS models that conditions the line in addition to providing backup?
 

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Powerware Model 9120 UPS conditions and has battery backup. It is more expensive than either off-line or line-interactive UPS's and it has a continuous sinewave output even during battery discharge. However, if any equipment supported by the UPS generates more than 10% current harmonics, voltage distortion may be a problem.


Inrush current will overload the UPS if inrush current exceeds max running current. If your amps limit inrush current, there will not be a problem. If inrush will occur, the UPS should either be sized to handle the inrush current (do not exceed 15A input current) or be aware that the UPS will go to bypass during inrush. Typically about 1500VA is the largest UPS you can plug into a 15A outlet.


Powerware offers UPS's similar to APC and is typically competitive with APC. Do an internet search and you should find Powerware products.


In my opinion UPS's do not condition as good as line conditioner that have low output impedance. Harmonic voltages are produced by non-linear loads such as switch mode power supplies used in some sub amps. The greater the output impedance of the UPS or line conditioner, the greater the voltage distortion for a given current distortion. A low impedance line conditioner will develope almost no voltage distortion on its output.


UPS's are current limited sources and as such may limit current below the peak current needed by your amps when playing loud music with heavy bass for instance. Check with the manufacturers of your equipment for maximum current draw and size your UPS to handle the worst case situation.
 

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Don't sweat perfect "sine-wave" power, because it doesn't make any difference to your amp. No one has ever published a double-blind test that demonstrates a measurable difference in output sound between line-conditioned power and "straight" AC power.


If the AC weren't converted to DC, you'd hear a difference, but the transformers and capacitors in your average power supply can deal with reasonably large variances without skipping a beat.


That might start a flame war, because it steps on the toes of the power conditioner believers, but oh well.


Bottom line? Skip expensive line conditioners, save your money, and get whatever UPS that APC recommends if you want to protect your system from power outages / brownouts.
 

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Discussion Starter · #11 ·
JTA:


Thanks for the advice.

I'll do a search for the Powerware product you mention.

APranger:


Thanks for your advice as well. The reason I'm looking for a power conditioning UPS is because here in Sri Lanka, the line voltages fluctuate quite a bit. From what I understand, regular UPSs switches to battery everytime the line power goes out of range. This, in turn, drains the battery and the battery may not have its complete potential during a power loss. Power losses are also quite frequent here.


Please correct me if I'm wrong, but I am of the impression that a conditioning UPS would resort to battery power ONLY during a power loss and NOT during voltage fluctuations. This preserves the complete battery potential for power outages.
 

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UPS's that rectify the incoming AC to DC and then invert the DC back to AC are called on-line or double conversion UPS's. Off-line and line-interactive UPS's do not go through this double conversion process. By rectifying and inverting, the UPS corrects both voltage and frequency variations. In the US frequency deviations are uncommon except when running on generator.

However, in some countries, both voltage and frequency changes are common. Only a double conversion UPS can correct both problems.

However, even the double conversion UPS will drop onto battery before the input voltage is totally gone. Usually this occurs at -20% to -30% low voltage. Which equates to a voltage drop of 24 volts to 36 volts on a 120 volt circuit. So, all UPS's are designed to go to battery at some point. Some go to battery at -10% while other as low as -30 to -40%. Some are load dependent. That is, they will accept a lower input voltage if they are lightly loaded.
 

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What sort of power losses are we talking here: 5 seconds? 5 minutes? More?


A UPS is really only the first line of defense against a power outage. They are designed for 5-15 minutes of runtime, typically, so that they can trigger a safe shutdown of a computer. Or, in your case, you'd be able to safely shut down your theater equipment.


If you want to watch TV & movies in the dark, you need to be looking at a fuel-powered backup generator to keep the power going. A UPS isn't going to cut it over long periods of time.


Otherwise, I wouldn't give serious concern to how often the UPS switches to battery power. They will recharge themselves during the "good power" periods. As long as your output voltage is consistent and uninterrupted then the UPS is doing it's job.
 
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