I own a APC 800va UPS . It has a stepped sinewave output . I use it with seasonic X-750W psu (it's Active Power Factor Correction). When there is a electric blackout. UPS reacts quickly, and pc doesnt shutdown. But there is an annoying buzzing sound coming from the PSU .

Some claim it's even worse than a shutdown ,and aPFC PSU's should only be used with pure sinewave UPS's.

Others claim that , buzzing sound doesn't matter at all , Active Power Factor Correction PSU work fine with stepped sinewave UPS's . Should i be using this UPS ?