Does the sine wave function of a UPS matter even when there is power from the grid?
I'm considering getting a UPS for my home studio computer (recent Mac Mini), router, sound card, speakers, and analog synths.
The purpose is just to save the equipment in case of a power outage, and give me enough time to shut everything down. The purpose is not to be able to keep on working with the equipment when there is no power.
I am considering getting a "sine wave" (i.e. non-stepped sine wave) UPS (perhaps something like the CyberPower ones, although I read that they may not provide a "pure sine wave.")
My understanding is that stepped sine waves may interact negatively with audio equipment and some computers. Since the equipment will constantly be plugged in behind the UPS regardless if there is power or not, I'm trying to understand to which degree a "sine wave" UPS is really necessary.
Does the UPS "sine wave" function matter ALL the time regardless if there is power or not, because the equipment is constantly plugged in behind the UPS, so not having UPS “sine wave” could/would disturb the audio quality even under normal operations with power from the electricity grid? In that case, "sine wave" seems virtually necessary to have.
Alternatively, does the UPS “sine wave” function matter ONLY when there is a power outage, in order to maintain close to normal functioning of the equipment? In that case, I imagine I can do without "sine wave" because I will not be using the audio equipment while on battery power.