I realize that this thread is 3+ years old now, but figured I would chime in & share my experience for others interested in using these Eaton double-conversion UPS for audio / hi-fi. Like sleepwalker65, I used an Eaton 9130 (PW9130L1500R-XL2U) -- picked it up for $150 on eBay from a corporate liquidator -- in excellent condition, all cables, but no batteries. (A set of four new batteries -- also from eBay -- added $83 to my cost.)
As sleepwalker65 notes, the Eaton 9130 UPS has 2-3 high volume, but ridiculously loud Sanyo Denki fans (1-2 80mm fans, depending on your model, and a 60mm fan). Unless you plan to locate the UPS remotely (as sleepwalker did) these will not work for your audio system -- the fan noise is deafening!
But you can replace the fans with relative ease. I replaced the 80mm fans with two Noctua NF-R8 redux-1800 fans in a push-pull setup, one sucking in air at the front, the other exhausting air out the rear. The 80mm Noctua fans run $13 apiece, they're super-quiet (17.1 dB) and move quite a bit of air -- not as much as the Sanyo Denki originals, but more than enough to keep the Eaton 9130 happy. Similarly, I replaced the 60mm Denki fan that was cooling the central heatsink with a Noctua 60mm Noctua NF-A6x25 FLX. (I don't think I used the Noctua LNA low noise adapters with any of the fans because I wanted maximum CFM. I had to modify the front faceplate a bit with my Dremel to get the front 80mm Noctua to fit, but not a big deal. I used one of the y-connectors that comes with the Noctua fans to tether the front & rear 80mm fans together from the same power source (the lead that was powering the original 80mm Denki, located at the rear of the UPS. I had to splice the power leads to adapt the Noctua fans to the Eaton power leads, as the plugs/connectors are not compatible.
Finally, I custom ordered a front dust filter ($8.00+shipping) from https://www.demcifilter.com that looks like it was made for the Eaton!
The end result? The UPS is now practically inaudible. It sits right in front of me (two feet away) on my desk under my monitor (with a 2U width TrippLite Isobar surge protector in between) and I cannot hear it at all. My PC makes more noise than the UPS. Heck, even the AC Infinity audio component fan I have on top of my integrated amplifier is noisier.
The Eaton 9130 silently powers my desktop PC, 42" LG monitor, the external backup drive, a NAD 3400 integrated receiver, the Denafrips IRIS DDC, the Peachtree iDac, an Outlaw ICBM subwoofer/bass manager, my Woo WEE electrostatic headphone converter, and an NAD 4300 tuner . . . and the total load never exceeds 10% of its 1500 amp capacity. (Plus, no fan alarms from the Eaton!)
Before undertaking this mod, I carefully studied Oscar Munoz' excellent blog about replacing the fans in his 9130 (https://translate.google.com/translate?sl=auto&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=https://www.it-como-hobby.com/index.php/2017/07/31/mod-ventiladore-sai-eaton-9130/). Also, Col. Sanders blog entry and following comments at https://ttlinkdiscussion.blogspot.com/2016/07/eaton-9130-2kva-1800w-full-conversion.html.
As I prepared to do the mod, I also found helpful info in one of the reviews on Amazon for the ARCTIC F8 Silent - 80 mm Case Fan (search the reviews for "5PX"), even though he chose the Arctic fan(s) for his Eaton UPS mod, rather than the higher volume Noctua fans.
Finally, you can find lots of helpful tips at https://www.reddit.com/r/homelab/comments/gna6vr/fan_replacement_for_eaton_ups. And searching Google or DuckDuckGo for "replacing fans in an eaton ups" will take you to numerous step-by-step guides and YouTube videos walking you through the process of opening up an Eaton UPS and replacing the fans (even though you'll be using plan different, quieter fans than the OEM.)
I'm pretty sure that this mod would also work with the Easton 9PX series (which replaced the 9130), but I haven't tried it since I don't own a 9PX UPS.
The final result -- for far, far less than a PS Audio regenerator -- is pure sine wave, double converted power with 9-factor power conditioning. I reckon I spent a total of $295 for the 9130, new batteries, fans and dust filter.
