Thanks very much, Greg. Those are logical questions, and yes, a UPS is a form of power regenerator.
However, for a number of reasons a conventional UPS would be unsuitable for use with an audio system. Those reasons include:
1)Some of them, especially the inexpensive ones, dont generate pure sine waves. They generate a stepped approximation to a sine wave, which most likely means that their output has far worse harmonic distortion than is present on the AC that is coming out of the wall.
2)Limited run time. I have 900 watt/1500 volt-amp pure sine wave UPS's on a couple of my computers. Their specs indicate a runtime when on batteries of 11 minutes when loaded at half capacity, and 2 minutes at full load. My computer setups each draw about 200 watts when not doing heavy processing. The UPS that is on each of those setups will power them for less than half an hour when on batteries.
3)Lead-acid batteries, which are what are used in conventional UPSs, dont like to be subjected to large numbers of deep discharge/charge cycles. That will severely degrade their useful life, as I understand it.
4)I would be concerned about rfi (radio frequency interference) they may generate, which could couple into the audio system either via power cords or through the air. Ive noticed that an AM portable radio will buzz fairly loudly when brought near my UPSs.
5)I would also question how well they would respond to high speed fluctuations in current demand that power amplifiers (other than Class A) will require.
Thanks again. Best regards,
-- Al