Orb user here. Got it from ebay. I've flattened thirty or forty records so far and they've all come out much better and although some still aren't perfect they play just fine. Saved me from the PITA of exchanging. Mine is rated 100-125 volts. As to audibility depending on the shape of the warp it's absolutely audible on my system. I have found the rate of change of the warp seems to be the most important factor...not sure if I'm wording that correctly. If you only have a few warped records I can't see the value unless you're OCD or have money burning a hole in your pocket.
How best to eliminate LP warps
I own about 2500 LPs, and I like to think they're flat. Furthermore, I espoused the view that warped LPs ought to be discarded. But lately I have found 2 or 3 of my LPs that do have warps but sound too good and are too precious for the music recorded on them to throw away. So I am in the market for ideas on how to remove warps. I am aware that there was a device on the market that looked like a large waffle maker, to be used for warp removal. I think Furutech made it, but I never see it advertised these days. I am also aware of the DIY method of placing an LP between two glass plates and heating the ensemble. The question there would be how hot and for how long? Any suggestions are welcome, especially opinions on the efficacy of the Furutech. Thanks. Please no comments on vacuum hold down; I think it's a great idea but none of my five turntables has that feature.