Only the "SmartUPS" series, model 700 and up of the APC UPS line(or any that I've seen, I think APC is the only one) output a pure 60Hz sinewave.
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Good Question Dekay. I too just purchased a SmartUPS 1000xl for my server and was thinking of plugging it in (to see if I noticed a benefit). After reading your concerns I'm hesitant to try. Platinumears ...O.k. so htese models put out a pure 60hz sinewave, but how's that relevant? Are you saying that these units are incompatible or compatible?
Dekay, I don't think a square wave fed into your audio equipment's power suppy would damage anything but I can think of an other reason or two why this would be a less than desireable thing to do. As a matter of fact I have seen the sinewave coming out of the wall in some cases look alot better than what came out of the "sine wave output" power conditioner when it was plugged in. I apologize for forcing my opinion on you but IMHO a dedicated outlet with a good ground will do you much better than a conditioner anyday.
I have been evaluating and using APC units for about 8 years now, in computer applications, and I have learned a few things about them that might be helpful.
Almost all APC units are of a type that does not continously regenerate power, this means that while clean AC is present at the input, they pass this AC through to their output unmodified. This AC is filtered, and there is surge protection, but other than that, there is not much else that is done to the AC. In addition, there is a battery charger that maintains the internal batteries at all times, and some control electronics. On most units I have seen, there is a tiny bit of RFI caused by the internals; it is not much, but it is meassurable (+/- .3 to 2V).
When the units switch to battery power, they essentially use the batteries to power an inverter in the unit. This inverter generates AC from the battery DC. The AC that is generated is very good under almost all circumstances I have seen; I extensively tested the 1200VA and up models, using osciloscope and various loads to judge the AC quality.
A few things I have noticed: The inverters run best under moderate load. A 1200VA APC had substantial AC distortion when run around 1200VA. The inverters do great with steady loads, but when load conditions vary widely, some spikes, frequency drift and RFI is noticeable. Computers in general are a nice, steady load... Audio equipment, especially heavy amps, are not. I would not be too confident the APC would do well while on battery and under heavy load. When the inverters get warm, and when batteries get low, the signal quality and stability are not as good. AC voltages on some units were a bit low when running the inverter. Finally, there is a tiny problematic period right after the unit switches to inverted power, and again right before it switches back to Straight AC. For all computer applications, this was no problem. It might very well be audible on a hifi system.
If you want to see how bad it can get, connect a laser printer in the off position to a UPS, run UPS on battery, and then turn the laserprinter on. If you look at a scope while doing this, you will be shocked. The UPS will probably also shut down.
Now, again, the APC UPS-es do NOT run their inverter all the time, ONLY when running on battery. So, until you switch to battery, you are getting a very expensive surge protector...
Dekay, after a previous correspondence with you, I did some searching at the PS Audio site about waveforms that are used in their PowerPlants. I just checked to make sure that what I remembered was true. PS Audio states that the perfect waveform for a power supply should be a square wave, BUT (and a big BUT) due to bandwidth limitations and the components of the square wave they should NOT be used in A/V equipment because they "would drive most power transformers crazy". Reading further it sounds like they would have included a square wave in their Multi-Wave units, but compromised with several other waveforms instead. I recommend you check out their site as well. I don't know what the APCs put out, but further investigation sounds like a pretty prudent idea.
This is the reply that I recieved from APC technical support: The Line R is purely a line conditioner. The Line R1250 has a load capacity of 1250 Watts. It's got boost and trim to step up low voltage and trim high voltage. The Line R also does not put out a pure sine wave. It puts out whatever wave is coming out of the wall. The nominal input frequency on the Line R is 50/60hz, and the nominal input voltage is 120Vac. I think that I will give it (the APC) a try on our mini system for starters (Sony MHC-NX1 running line out to a Musical Fidelity X-A1 to Polk RT-15's in a, very close, near field setup) and see how it sounds. It's not Hi-fi but it does resolve enough to differentiate between most cables and wire, I have found. Thanks for all of the input which enabled me to ask the right questions.