Interesting..., This post from a guy on Audiogon ( https://forum.audiogon.com/discussions/carver-hta5a ) seems to indicate that the Factor Electronics amp is identical to the "OSD Audio XA 5180..., albeit apparently with some confusing power specs (maybe even incorrect specs) between the two.
I have ZERO information beyond the research I'm posting here..., TheCarverSite focuses on the vintage Bob Carver gear from the 80's and 90's production, all built with Bob Carver's designs. Note that the Brand "Carver" was purchased by Phoenix Audio, then sold again, (and again..., probably)..., so it's a long shot or anyone's guess on how it got here.
Another search found the manual to the OSD version of the same amp..., here: https://www.outdoorspeakerdepot.com/mm5/graphics/pdfs/OSD-XA5180-Amplifier-Manual2020.pdf
That may be helpful..., maybe not...,
I tried searching for the HTA50 manual, only one site had it, but it required too much effort http://ServiceManuals.net (purchase, registration, etc..., I avoid those sites.)