Because of Purepower 3000 power was not enough for my high power ss system then I bought an ABB 18KW UPS.
Both APC and ABB are popular and my friend used APC and the sound of APC was not good and I choosed ABB to test between Wall AC and ABB.
ABB from Switzerland produce high quality UPS and last week I have listened to one of them (ABB 20KVA model) in my system.
After break-in process I have connected different parallel loads (500w, 4000w, 5700w) to ABB UPS to view what happen to sound quality.
ABB UPS vs Wall AC Power (when wall AC is good) :
ABB is like high power low impedance Mark Levinson Amplifier : clean but Compress , thin and damaged harmonics.
Wall AC power (when AC is good) is like Zero feedback good Amplifier : Rich Harmonic, dynamic and better more 3D Image
ABB has no limits in current delivery (18,000W , 100A) and it has superb jump and attack but no decay no harmonic no life in music.
you can feel the compression of sound when the ABB in online.
I do not know but I guess most UPS and Inverters like ABB , APC , ... use feedback to regulate voltage and their sound reminds me bad Computer playbacks.
Purepower is like bragin and If Richard had a 30,000VA purepower then I was his first customer. I told richard if he can help me to design a high power Purepower but I think it is not possible to him.
Totally I think no UPS in this market is good for sound.
In the next step I will go for testing Kevin power System. 12v battery + 6 parallel Victron Energy (total 18000VA).
If Victron will not be good then I will go for delicated 20/000v to 380v transformer .